mf/samplegrabber: Handle paused state.
The following behaviors from Windows are implemented:
* Transitions from STOPPED to PAUSED are forbidden;
* Sample requests are only emitted for transitions from STOPPED to
RUNNING (i.e., not when transitioning from PAUSED);
* Transition events are emitted again when transitioning from a
state to the same state, except when such state is PAUSED.
Signed-off-by: Giovanni Mascellani <gmascellani@codeweavers.com>
Signed-off-by: Nikolay Sivov <nsivov@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>