quartz: Process motion events within windows bounds without window set

quartz: Process motion events within windows bounds without window set

When an NSEvent does not have the window field set, we already assumed
the event was not for us and discarded it.  But for NSMouseMoved events
we now make an exception, because such events generated after
using/clicking the main menu bar have the window field set to NULL while
the application window still has focus.

We used to experience a loss of motion events after using the menu bar,
this could be seen in buttons that stopped prelighting and first
clicks often being ignored unless you clicked somewhere else first.
These issues are fixed by this patch.