Inverts the given channels of the base image.
Mode may contain the characters "r", "g", "b", "a".
Only the channels that are mentioned in the mode string will be inverted.
Changes:
* Fix indentation.
* Pass strings by const reference.
* Merge Strfnd and WStrfnd into one class instead of copying them.
* Remove trailing spaces.
* Fix variable names.
* Move to util.
* Other miscellaneous style fixes.
* Rename everything.
* Strip J prefix.
* Change UpperCamelCase functions to lowerCamelCase.
* Remove global (!) semaphore count mutex on OSX.
* Remove semaphore count getter (unused, unsafe, depended on internal
API functions on Windows, and used a hack on OSX).
* Add `Atomic<type>`.
* Make `Thread` handle thread names.
* Add support for C++11 multi-threading.
* Combine pthread and win32 sources.
* Remove `ThreadStarted` (unused, unneeded).
* Move some includes from the headers to the sources.
* Move all of `Event` into its header (allows inlining with no new includes).
* Make `Event` use `Semaphore` (except on Windows).
* Move some porting functions into `Thread`.
* Integrate logging with `Thread`.
* Add threading test.
Move debug streams to log.cpp|h
Move GUI-related globals to clientlauncher
Move g_settings and g_settings_path to settings.cpp|h
Move g_menuclouds to clouds.cpp|h
Move g_profiler to profiler.cpp|h
