Noted by XXX comments that the XFlush() calls probably shouldn't be there.

Noted by XXX comments that the XFlush() calls probably shouldn't be there.
Flushing the X protocol stack every little bit both adds clutter to the
code and may impede performance.

It seems that we should be able to get rid of these, though
allowing client code to directly call glutMainLoopEvent() does make it
a little more complicated.

Something to ponder.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@279 7f0cb862-5218-0410-a997-914c9d46530a