Thread class fixes.
Win32 threads
Tweaking stuff related to threads/windows
Win32 threads not terminating properly
Fixing issue with Win->IsOpen() (see ext desc)
IsOpen() was always returning true on a window that was closed on another
thread. Strange. Works now on Win32, need to do testing on X11
Merge branch 'palistov_window'

Conflicts:
	src/core/Window.cpp