Rewrite requires renderless mode in the VMR7, which means that it needs to
actually use ddraw instead of d3d9. At that point the two will share almost no
common code. Split them into separate objects which live in separate files.

This commit essentially copies vmr9.c into vmr7.c, then removes the
VMR7-specific interfaces from the VMR9 and vice versa. The default presenter is
retained for now (but will be replaced eventually).

Since the VMR7 no longer exposes IVMRSurfaceAllocatorNotify9, the relevant calls
to AdviseNotify(), SetD3DDevice(), and AllocateSurfaceHelper() are changed from
COM methods to direct function calls. No other change should be made.