- fixed a minor bug in the UNIX/X11 cursor code, causing an X error and abort

  due to a stale cursor cache, when the application (which calls glutSetCursor),
  uses glutLeaveMainLoop to close the connection to the X server, and then
  re-initializes freeglut and starts over with a new connection.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1749 7f0cb862-5218-0410-a997-914c9d46530a