WM_SETFOCUS should not change focus to child instead, then all input goes to child...

WM_SETFOCUS should not change focus to child instead, then all input goes to child even if it should go to parent. Mousewheel needed to check if actually in child, other mouse action (move, press) are automatically passed to child

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1516 7f0cb862-5218-0410-a997-914c9d46530a