Move some UUIDS to "moreuuids.h".
Cosmetic: Declare a GUID constant for Morgan's Stream Switcher.
Cosmetics: Try to use CLSID constants when available.
Subtitle input pin: remove a useless lock.
Prevent black lines from appearing on the sides of the video when resizing.

This happened mostly when resizing manually or when using auto-fit zoom.

Fixes #2423.