minor changes to ghost
- use WITH_ASSERT_ABORT define, so GHOST_ASSERT will abort.
- rename XTablet -> GHOST_TabletX11, was confusing since it was named like an xlib struct.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53832 954f8c5b-7b00-dc11-b283-0030488c597c