Update the Changelog.
CVobSubFile: Deobfuscation in ReadIdx.
Improve the speed of subtitles toggling (on/off) and switching.

Avoid reloading the subresync bar if the same subtitles were already loaded.

This commit fixes #3650.
Use conversion constructors to work-around confusing AStyle styling.
Use a bitcheck instead of casting (WIP).

Fixes CID #965944.