* switch travis to trusty
* new parameter fullscreendesktop: uses desktop resolution for fullscreen
* "colorbits" removed, since it's no longer supported
* scr_w/scr_h no longer necessarily reflect the true display resolution
(with fullscreendesktop = 1 and fullscreen = 1, scr_w and scr_h are
ignored)
* desktopw and desktoph are now guaranteed to have nonzero values
* fallback to old mouse behaviour when SDL_SetRelativeMouseMode fails
* require a click into the window to grab the mouse
* scr_w/scr_h default to desktop resolution on first run
thx sauerbraten :)
DOCREF fullscreendesktop colorbits
