Additional changes that were required for the feature:
1) focusing on the pointed window in full screen mode
2) In X11 - handling events that occur during keyboard ungrabbing
3) In X11 - handling Leave/Enter Notify events that occur during keyboard grabbing/ungrabbing
4) In X11 - fix for focus events that are handled in the wrong order (happens when
focus events occur during grabbing the keyboard)
5) In X11 - ignoring key release events during key holding
6) In Windows - synchronizing keyboard release events that occured during a modal loop
