GUI for selecting a screen
fixes
use KEY_* instead of the char value
test
only warp mouse when neccessary; use absolute positions
hide system cursor for now
fix transition between MOUSE_MODE_WARP_CENTER and MOUSE_MODE_NONE
remove dbg output
hide cursor again; remove old code
hardware cursor, finally
Merge branch 'hardwarecursor' into sdl2all
Merge branch 'master' into sdl2all
Merge branch 'master' into sdl2all
Merge branch 'master' into sdl2all
initial clipboard support
Merge branch 'clipboard' into sdl2all

Conflicts:
	src/engine/client/input.h
Merge branch 'master' into sdl2all
Merge branch 'master' into sdl2all

Conflicts:
	src/engine/client/backend_sdl.cpp
Merge branch 'master' into sdl2all

Conflicts:
	src/engine/client/backend_sdl.cpp
Merge branch 'master' into sdl2all