FFAudioDecoder: fix audio decoding for new ffmpeg updates.
Updated Catalan translation.

Refs: #2408.
RFS: Update to the GPLv2+ license.

The RARFileSource license is now compatible with GPLv3.
Updated French translation.
Fix: Play > Subtitles > Styles menu entry was incorrectly enabled/disabled.

This was broken in 0615b154c1a9e6289234a5acb6c2360b1560577c.

This commit fixes #2978.
Update Readme.md
Initialize variables in the constructor.
Cppcheck fixes:

* reduce variable scope
* remove unneeded variable assignments
update Little CMS to v2.5 (git a4847b0)
Fix camelcase word "Charset".