Adding Mac OSX to the list of platforms covered by the X11 support. This is a stopga...

Adding Mac OSX to the list of platforms covered by the X11 support.  This is a stopgap measure so we can get something out the door; I would prefer native OSX support.  See e-mail from Paul Martz at 3:25 PM, 11/16/09 for some thoughts on this.  Apparently this allows the library to build but the demos do not work.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@850 7f0cb862-5218-0410-a997-914c9d46530a