Pure code janitoring: Shuffled the order of some of the case statements

Pure code janitoring: Shuffled the order of some of the case statements
in the UNIX_X11 X event processing loop.  (In general, it's nice to have
case statements sorted, especially when you have a *huge* switch statement
like this.  That makes it easier to find the one that you're looking for,
and to see if a certain case is defined...)

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@320 7f0cb862-5218-0410-a997-914c9d46530a