Quick fix for issue #193
Locks window size to 1024x768 on OSX and requests that size on X11 displays.  The X11 window manager can entirely ignore the request so this doesn't fully resolve the issue on OSX.
Merge pull request #196 from libRocket/hotfix/193-sample-resize-bug

Quick fix for issue #193, attempts to lock window size to 1024x768 as Windows shell does