Log Message:
Update misc/tmux to 2.4.

Incompatible Changes
====================

* Key tables have undergone major changes. Mode key tables are no longer
  separate from the main key tables. All mode key tables have been removed,
  together with the -t flag to bind-key and unbind-key.

  The emacs-edit, vi-edit, emacs-choose and vi-choose tables have been replaced
  by fixed key bindings in the command prompt and choose modes. The mode-keys
  and status-keys options remain.

  The emacs-copy and vi-copy tables have been replaced by the copy-mode and
  copy-mode-vi tables. Commands are sent using the -X and -N flags to
  send-keys. So the following:

    bind -temacs-copy C-Up scroll-up
    bind -temacs-copy -R5 WheelUpPane scroll-up

  Becomes:

    bind -Tcopy-mode C-Up send -X scroll-up
    bind -Tcopy-mode WheelUpPane send -N5 -X scroll-up

  These changes allows the full command parser (including command sequences) and
  command set to be used - for example, the normal command prompt with editing
  and history is now used for searching, jumping, and so on instead of a custom
  one. The default C-r binding is now:

    bind -Tcopy-mode C-r command-prompt -p'search up' "send -X \ 
search-backward '%%'"

  There are also some new commmands available with send -X, such as
  copy-pipe-and-cancel.
* set-remain-on-exit has gone -- can be achieved with hooks instead.
* Hooks: before hooks have been removed and only a selection of commands now
  have after hooks (they are no longer automatic). Additional hooks have been
  added.
* The xterm-keys option now defaults to on.

Normal Changes
==============

* Support for mouse double and triple clicks.
* BCE (Background Colour Erase) is now supported.
* All occurrences of a search string in copy mode are now highlighted;
  additionally, the number of search results is displayed. The highlighting
  updates interactively with the default emacs key bindings (incremental
  search).
* source-file now understands glob patterns.
* Formats now have simple comparisons:

    #{==:a,b}
    #{!=:a,b}

* There are the following new formats:

  - #{version} -- the tmux server version;
  - #{client_termtype} -- the terminal type of the client;
  - #{client_name} -- the name of a client;
  - #{client_written} -- the number of bytes written to the client.

* The configuration file now accepts %if/%endif conditional blocks which are
  processed when it is parsed; the argument is a format string (useful with the
  new format comparison options).
* detach-client now has -E to execute a command replacing the client instead of
  exiting.
* Add support for custom command aliases, this is an array option which
  contains items of the form "alias=command". This is consulted when an
  unknown command is parsed.
* break-pane now has -n to specify the new window name.
* OSC 52 support has been added for programs inside tmux to set a tmux buffer.
* The mouse "all event" mode (1003) is now supported.
* Palette setting is now possible (OSC 4 and 104).
* Strikethrough support (a recent terminfo is required).
* Grouped sessions can now be named (new -t).
* terminal-overrides and update-environment are now array options (the previous
  set -ag syntax should work without change).
* There have been substantial performance improvements.