Fix: Possible double free when resetting PGS subtitles.

This resulted in random crashes when seeking quickly in a file with PGS subtitles and other various cases.

Fixes #4240.
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Fixes #4268.
Don't prevent the users from using the ISR if they choose not to block VSFilter like filters.

This commit fixes ticket #4231.
PGS subtitles: Enqueue empty segments to be sure subtitles are properly cleared when using the queue.

This is a work-around and will be improved later.

Refs: #3691.
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Update files for v1.7.5 release.
Update docs/Release.txt.
Set MPC_NIGHTLY_RELEASE to 1.
Readme.md: switch to SVG badge.
ISR: Disable "Save subtitle" command when it's unsupported.

Based on Kasper93's patch.
Cosmetic: Prefix (smart) pointers with p in SubtitleInput struct.

It's clearer that way.
Use AtlEscapeUrl/AtlUnescapeUrl to do URL encoding/decoding.

This is now available outside of ATL Server. It avoids using our incomplete URL encoding function.
PGS subtitles parser: Use CAutoPtrList to avoid manipulating raw pointers.
DVB subtitles parser: Use CAutoPtrList to avoid manipulating raw pointers.
Updated LAV Filters to 0.61.2-11-g70ec47a (custom build based on 0.61.2-6-002d1f2)

Important changes:
 - LAV Splitter: Alternate audio support for HLS (ticket #3575)
 - LAV Video: Support VP7 video
 - LAV Video: Use the MediaFondation WMV decoder on Windows 7+ instead of the DMO WMV decoder
 - Updated ffmpeg and libbluray libraries
Fix: Two private interfaces had the same UUID.

Requesting IBDATuner succeeded even if the interface wasn't implemented since it had the same UUID than IGraphBuilderDeadEnd.

Fortunately this had no visible effect thanks to additional checks.
Renderer statistics: Hide an unneeded line when VSync is disabled.
PGS/DVB subtitles: Simplify the code.

Use only 3 classes instead of 4. Will be useful for some future work.
Fix: Changing the zoom level didn't leave fullscreen anymore after 54d1fa7cd5d3cd448c663033a35e756847de6bad.

This commit fixes #4288.
StatusLabel: flickerless paint