Set #4:

  * Fixes a couple of compiler warnings and other bugs.
  * freeglut_main.c: Removes a compiler warning
  * freeglut_structure.c: Sets the current window before calling the window closure callback
  * Possibly other changes

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@71 7f0cb862-5218-0410-a997-914c9d46530a