Log Message:
Update devel/jenkins to 2.25.

Based on a PR by Jussi Sallinen. Switch to the weekly release
branch and prepare to share framework with devel/jenkins-lts.

Upstream changelog follows (LTS backports up to 2.7.4 excluded).

What's new in 2.25 (2016/10/09)
- Display transient actions for labels.
- Add user to restart log message for restart after plugin
  installation.
- Internal: Code modernization: Use try-with-resources a lot more

What's new in 2.24 (2016/10/02)
- Show notification with popup on most pages when administrative
  monitors are active.
- Allow disabling/enabling administrative monitors on Configure
  Jenkins form.
- Ensure exception stacktrace is shown when there's a
  FormException.
- Add new jenkins.model.Jenkins.slaveAgentPortEnforce system
  property, which prevents slave agent port modification via
  Jenkins Web UI and form submissions.
- Indicate hovered table row on striped tables.
- Decrease connection timeout when changing the JNLP agent port
  via Groovy system scripts.
- Added Serbian locatization.
- Exclude /cli URL from CSRF protection crumb requirement, making
  the CLI work with CSRF protection enabled and JNLP port
  disabled.
- Prevent instatination of jenkins.model.Jenkins on agents in the
  ProcessKillingVeto extension point.
- Fix handling of the jenkins.model.Jenkins.slaveAgentPort system
  property, which was not honored.
- CLI: Disable the channel message chunking by default. Prevents
  connection issues like java.io.StreamCorruptedException: invalid
  stream header: 0A0A0A0A.
- CLI: Connection over HTTP was not working correctly.

What's new in 2.23 (2016/09/18)
- Fix JS/browser memory leak on Jenkins dashboard.
- Build history was not properly updating via AJAX.
- Properly enable submit button on New Item page when choosing
  item type first.

What's new in 2.22 (2016/09/11)
- Change symbol and constructor for SCMTrigger to pollScm to make
  it usable in Pipeline scripts.
- Prompt user whether to add the job to the current view.
- Update to sshd module 1.7, allowing definition of client idle
  timeout.
- Update to sezpoz 1.12 with better diagnostics.
- Fix NullPointerException when descriptor is not in
  DescriptorList.
- Use the correct 'gear' icon for Manage Jenkins in Plugin
  Manager.

What's new in 2.21 (2016/09/04)
- Ask for confirmation before canceling/aborting runs.
- Add newline after the text in userContent/readme.txt.
- Fixed the missing icon in the System Script console.
- Print warnings to system logs and administrative monitors when
  Jenkins initializarion does not reach the final milestone.
- Developer API: UpdateSite#getJsonSignatureValidator() can be now
  overriden and used in plugins.

What's new in 2.20 (2016/08/28)
- Make Cloud.PROVISION permission independent from
  Jenkins.ADMINISTER.
- Allow the use of custom JSON signature validator for Update Site
  metadata signature checks.
- Do not process null CRON specifications in build triggers.
- Setup wizard now checks if the restart is supported on the
  system before displaying the restart button.
- Test Windows junctions before Java 7 symlink in symbolic link
  checks.
- Fixed background color in the ComboBoxList element in order to
  make options visible.
- Fixed editing default view description with automatic refresh.
  System message is not being displayed instead of the view
  description.
- Fixed process tree management logic on Solaris with 64-bit JVMs.

What's new in 2.19 (2016/08/21)
- Prevent resource leaks in AntClassLoader being used in the core.
- Fix the wrong message about empty field in the case duplicate
  item name in the New Item dialog.
- Allow invoking Upgrade Wizard when Jenkins starts up. It can be
  done by placing an empty
  jenkins.install.InstallUtil.lastExecVersion file in JENKINS_HOME.
- Replace repetitious "website" and "dependencies" text in the
  Setup Wizard by icons.
- Expose Job name to system logs when Jenkins fails to create a
  new build with IllegalStateException.
- Downgrade Queue#maintain() message for dead executors during
  task mapping from INFO to FINE.

What's new in 2.18 (2016/08/15)
- Better diagnostics and robustness against old ChangeLogAnnotator
  API usage in plugins. Enhances JENKINS-23365 fix in 1.569.
- Prevent open file leak when the agent channel onClose() listener
  writes to the already closed log.
- Massive cleanup of issues reported by FindBugs. User-visible
  issues - wrong log message formatting bugs in the Update Center
  and user creation logic.
- Remoting 2.61: JNLP Slave connection issue with JNLP3-connect
  when the generated encrypted cookie contains a newline symbols.
- Remoting 2.61: Retry loading classes when remote classloader
  gets interrupted.
- Remoting 2.61: Improve diagnostics of Local Jar Cache write
  errors.
- Remoting 2.62: Be robust against the delayed EOF command when
  unexporting input and output streams.
- Remoting 2.62: Cleanup of minor issues discovered by FindBugs.
- Remoting 2.62: Improve class filtering performance in remote
  invocations.
- Remoting 2.62: TCP agent connection listener now publishes a
  list of supported agent protocols to speed up the connection
  setup.
- Improve German, Lithuanian and Bulgarian translations.

What's new in 2.17 (2016/08/05)
- Don't load all builds to display the paginated build history
  widget.
- Add dagnostic HTTP response to TCP agent listener.
- Internal: Invoke FindBugs during core build.

What's new in 2.16 (2016/07/31)
- Fix plugin dependency resolution. Jenkins will now refuse to
  load plugins with unsatisfied dependencies, which resulted in
  difficult to diagnose problems. This may result in errors on
  startup if your instance has an invalid plugin configuration,
  check the Jenkins log for details.
- Decouple bouncycastle libraries from Jenkins into
  bouncycastle-api plugin.
- Upgrade to instance-identity module 2.1.
- Hide the Java Web Start launcher when the TCP agent port is
  disabled.
- Allow admins to control the enabled agent protocols on their
  instance from the global security settings screen.
- Display delete button only when build is not locked.
- Use build start times instead of build scheduled times in build
  timeline widget.
- Internal: Move CLI commands wait-node-online/wait-node-offline
  from core to CLI module.
- Internal: Allow accessing instance identity from core.
- Internal: Fix the default value handling of
  ArtifactArchiver.excludes.

What's new in 2.15 (2016/07/24)
- Tell browsers not to cache or try to autocomplete forms in
  Jenkins to prevent problems due to invalid data in form
  submissions. From now on, only select form fields (e.g. job name)
  will offer autocompletion.
- Prevent null pointer exceptions when not entering a cron spec
  for a trigger.
- Defend against some fatal startup errors.
- Use the icon specified by the computer implementation on its
  overview page.
- Internal: Extract the CLI command offline-node from core.

What's new in 2.14 (2016/07/17)
- Minor optimization in calculation of recent build stability
  health report.
- When a user aborts the build, this user may be restored after
  its deletion.
- Prevent potential NullPointerException in the
  BlockedBecauseOfBuildInProgress build blockage cause
  visualization.
- CLI commands quiet-down and cancel-quiet-down were extracted
  from the core to CLI.
- Developer API: Extract listing of computer names to the
  ComputerSet#getComputerNames() method.
- Developer API: Add a try with resources form of impersonation.
- Developer API: Usage of ItemCategory#MIN_TOSHOW in external
  plugins is now restricted.

What's new in 2.13 (2016/07/10)
- Eliminate "dead executor" UI appearing after certain errors,
  such as JENKINS-27530.
- Make setup wizard installation panel usable on small screens.

What's new in 2.12 (2016/07/05)
- Enable the DescriptorVisibilityFilters for ComputerLauncher,
  RetentionStrategy and NodeProperty.
- Before starting a process, ensure that its working directory
  exists.
- Prevent NullPointerException during SCM polling if
  SCMDecisionHandler returns null veto.
- Fix optional plugin dependency version resolution.
- When creating a tar file, ensure that the final size does not
  exceed the value in header in the case of growing files.
- Do not inject build variables into Maven process by default for
  new projects.
- Update BUILD_TAG environment variable description to mention the
  replacement of slashes with dashes.
- Internal API: Make BulkChange auto-closeable.

What's new in 2.11 (2016/06/26)
- Provide an extension point for SCM decisions such as whether to
  poll a specific job's backing repository for changes.

What's new in 2.10 (2016/06/19)
- Better exception message if a SecurityRealm returns null when
  loading a user.
- Prevent NullPointerException in user registration if user ID is
  not specified.
- Internal: It was impossible to build Jenkins on 32-bit Linux
  machine.

What's new in 2.9 (2016/06/13)
- Remoting 2.60: Do not invoke PingFailureAnalyzer for
  agent=>master ping failures.
- API: Allow delegating TaskListener creation to build agent
  implementations.