GilSafeSingleLock(g_graphicsContext): UI unresponsive

There is, IMHO, something fishy with GilSafeSingleLock.

I have cases of the UI being unresponsive and I think it is due to a kind of race between 2 addons.
One of the is doing a window operation, so a GilSafeSingleLock is created but by the time the lock on g_graphicsContext is got, it takes ages to get the GIL back, resulting in a frozen UI.

Is it supposed to be so?

Pull request created: https://github.com/xbmc/xbmc/pull/1204