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)
External filters: Use two separated list for x86 and x64.

x86 filters only work with MPC-HC x86 and vice-versa.
Add some options to give a finer control on subtitles track selection.

The user is now free to choose if MPC-HC must prefer forced/default subtitles tracks (default is on) and if MPC-HC is allowed to change the subtitles track an external splitter selected to be the default (default is off).
Fix: The external filters list was lost when switching from registry to ini or vice-versa.
Cosmetics: Use directly m_s instead of AfxGetAppSettings() when possible.
PPageSubMisc: cosmetics.

* Use more meaningful functions names.
* Use correct visibility for the members variables and functions.