Fixing problem with non-client area becoming unresponsive on Windows due to mouse capture that isn't released. Thanks Philipp Kutin (on list!) for figuring this out and proposing a solution.
-> It appears GetAsyncKeyState's return can be non-zero even when the queried key is not pressed

git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk/freeglut@1627 7f0cb862-5218-0410-a997-914c9d46530a