Remove trailing whitespaces from some files

[ci:skip]
Update some build dependencies
Fix some compilation problems on Gentoo.

Closes GH-1261.
Fix a request handling crash on onAppInputChunk

Closes GH-1250.
Fix printing error IDs in the RequestHandler
Update CHANGELOG and credit Jacob Elder.
Introduce a Group-specific UUID that changes on every restart.

Allows Union Station to track server restarts, web server restarts
and application restarts. Closes GH-1258.
Fix user and group info lookup

Apparently _SC_GETPW_R_SIZE_MAX/_SC_GETGR_R_SIZE_MAX are not maximums:
http://tomlee.co/2012/10/problems-with-large-linux-unix-groups-and-getgrgid_r-getgrnam_r/
Closes GH-1253.
Introduce the `spawn_failed` hook.

Closes GH-1252.
Fix shared library creation on Sun Studio

Closes GH-1260.
Fix crash when the hook_spawn_failed hook is not set
Introduce various new components in preparation for future optimizations.
Add a faster way to detect whether we're on the event loop thread, using thread-local variables
Optimization: use boost::container::vector instead of std::vector in ApplicationPool2 for post lock actions

The Boost version does not allocate memory in its default constructor.
Optimize the priority queue in ApplicationPool2.

Replace the fibonacci heap with a d-ary heap. The former is an in-place data
structure that's backed by a vector, and thus has great CPU caching behavior.
This makes it perform better than a fibonacci heap despite worse algorithmic complexity.
Temporarily remove travis.yml
Remove mutex from FileChangeChecker and CachedFileStat. We don't need them to be thread-safe
Optimize ApplicationPool2 GetCallback

Use a simple struct functor instead of boost::function.
This is much faster.
Optimize ApplicationPool2 needsRestart()

Apparently CachedFileStat and FileChangeChecker are slow.
Fix pushWaiter() in ApplicationPool2

It may not call the callback inside the lock