When switching to game mode under X11, no ConfigureNotify event will

When switching to game mode under X11, no ConfigureNotify event will
happen and consequently no reshape callback will ever be called via
the normal mechanism. To fix this, note that the game mode window
needs to be resized and handle this before redraw.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@622 7f0cb862-5218-0410-a997-914c9d46530a