be more careful about closing menus when focus changes. Only do so when new focus...

be more careful about closing menus when focus changes. Only do so when new focus window is not ANY of the open menus and when it is not the menu's parent window (all open menus are guaranteed to have the same parent in my reading of the code)
Also simplified situation in which menus are SW_SHOWed... if a gamemode window is open, it must the parent of any active windows as there can be no other windows open on top of the gamemode window.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1716 7f0cb862-5218-0410-a997-914c9d46530a