quartz: Destroy BaseFilter after child class.

[Thomas Faber]

For the AsyncReader, this is a use after free on the critical section
again.

The NullRenderer doesn't have any pins, so that change is mostly
cosmetical to align it with the other classes.

The Parser change fixes a memory leak in addition to the use after free,
because AVISplitter_Release manually decrements the refCount and calls
Parser_Destroy instead of using Parser_Release -- so the filter's
members were never released in this code path.