Add bogus stabs for fullscreen window mode for BGE in GHOST. Platform maintainers should change these to replicate X11 behaviour. Also moved X11 implementation to public methods, just like the IWindow interface. Should fix compilation

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54813 954f8c5b-7b00-dc11-b283-0030488c597c