Log Message:
Changes 2.5:

Here are major changes since 2.4:

* we've moved to github!

* Bryan Chan has contributed s390x support

* stacktrace capturing via libgcc's _Unwind_Backtrace was implemented
  (for architectures with missing or broken libunwind).

* "emergency malloc" was implemented. Which unbreaks recursive calls
  to malloc/free from stacktrace capturing functions (such us glib'c
  backtrace() or libunwind on arm). It is enabled by
  --enable-emergency-malloc configure flag or by default on arm when
  --enable-stacktrace-via-backtrace is given. It is another fix for a
  number common issues people had on platforms with missing or broken
  libunwind.

* C++14 sized-deallocation is now supported (on gcc 5 and recent
  clangs). It is off by default and can be enabled at configure time
  via --enable-sized-delete. On GNU/Linux it can also be enabled at
  run-time by either TCMALLOC_ENABLE_SIZED_DELETE environment variable
  or by defining tcmalloc_sized_delete_enabled function which should
  return 1 to enable it.

* we've lowered default value of transfer batch size to 512. Previous
  value (bumped up in 2.1) was too high and caused performance
  regression for some users. 512 should still give us performance
  boost for workloads that need higher transfer batch size while not
  penalizing other workloads too much.

* Brian Silverman's patch finally stopped arming profiling timer
  unless profiling is started.

* Andrew Morrow has contributed support for obtaining cache size of the
  current thread and softer idling (for use in MongoDB).

* we've implemented few minor performance improvements, particularly
  on malloc fast-path.