Implement helper functions balanced_wait_until and balanced_awaken
They include new path for Windows 8.1+ (WaitOnAddress)
shared_mutex, cond_variable, cond_one, cond_x16 modified to use it
Added helper function utils::popcnt16
Replace most semaphore<> with shared_mutex
*Implemented 'cellMouse*' functions from 'sys_io' module, which are part
of the libmouse library.
* Added corresponding entries in the 'Config > Settings' menu to change
the handler of the mouse. Supported handlers: Windows, Null.
* cellGifDec: Fixed some errors and added support for RGBA color.
(Remember: The mouse support is very experimental)