MpaDecFilter: updated DeliverBitstream function, cosmetics.
Fix: "Once" and "Every time" menu entries weren't correctly disabled.

This was broken after ed77173416a73a207d8816918bb4e4b7facfd599.
Blacklist Accusoft PICVideo M-JPEG Codec 2.1 since causes a DEP crash.

Newer versions of the decoder have a different CLSID and don't crash.
Cosmetics: add missing brackets and consistently use .0f instead of .f.
Some testing on SetAlwaysOnTop. (not working)