MpaDecFilter: missing "return S_OK;"
update Release.txt
update Little CMS to v2.5 (git d504603)
CONTRIBUTING.md: mention the precommit hook script
Readme.md: switch to Atx-style headers
Readme.md: minor improvements
MpaDecFilter: Fix incorrect safety checks.
Some testing on SetAlwaysOnTop. (not working)
PPageExternalFilters: cosmetics.

* Use more meaningful functions names.
* Use correct visibility for the members variables and functions.
Playlist: Scroll and select the latest added item.

This commit fixes #2987.
Playlist: Put MPC-HC on top and give the focus to the playlist after a drag-and drop.