Rewritten code for auto-load subtitles and support for '_' as a separator.

Being a video file named video.ext, video_whatever.srt will now be auto-loaded.

This commit fixes #3195.
Give "Prefer external subtitles over embedded subtitles" option precedence over language matches.
Updated Little CMS to 4eb0140
Update Unrar to 5.0.0 (stable).
Fix auto-loading subtitles for video filenames containing special characters.

After 8c16873c8e6af244bed48e0ca446ec51e033c01f, auto-loading subtitles could fail or give wrong results for video filenames containing the following characters: !-.^+{}[]()$.

This commit fixes #3433.
Initial subtitle track selection: Update the special internal splitter case for LAV Splitter.

If the internal splitter has its own language preferences set, we won't override its choice.
Skip initial audio track selection process if only one track is available.
AudioSwitcher: Group tracks based on the status reported by the underlying IAMStreamSelect interface.

Will be used later.
AudioSwitcher: Output a pointer to the underlying filter for tracks sharing one pin.

Will be used later.
Initial audio track selection: Override splitter choice only for the internal splitter if no preferences have been set at that level.

An option will be added later to turn off that behavior.
Move the option "Allow overriding external splitter choice" to playback page and use it to control audio and subtitle tracks.

This commit fixes #3316.
MainFrm: Use GetFileName() when saving subtitles.

Fixes cases where URLs are being used as a suggested subtitle filename.
installer: Update Inno Setup's Basque translation.
PPageFileMediaInfo.cpp: Fix mismatching allocation and deallocation.

This was introduced in ecf6198ea30fb8888060360fa650b36c1c67cc69.
Update coverity version.
Update lcms2 to ad2cb04.
WebUI: Update normalize.css.
IsISO639Language: Fix a memory leak detected by Coverity.
Internal filters page: Add buttons to access filters properties.
WebClientSocket: Fixed case where return value of AsyncReader::Length() was not checked.

As reported by Coverity in CID 1084352.
Change PPageFileInfoDetails for consistency.