A subwindow in an Fl_Tile did not work well after recent addition of support for true Mac OS X subwindows.
The tile demo program runs correctly again.

git-svn-id: http://seriss.com/public/fltk/fltk/branches/branch-1.3@10453 ea41ed52-d2ee-0310-a9c1-e6b18d33e121