runtime window and event manager configuration

Variables
static bool	Fl::cfg_win_cocoa = 0
	Cocoa window management available, usually on OS X systems.
static bool	Fl::cfg_win_win32 = 0
	Windows window management available, on low level Windows.
static bool	Fl::cfg_win_x11 = 0
	X11 window management available, usually on Linux systems.

Detailed Description