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.
Update translations from Transifex:

 - Croatian
 - Dutch
 - German
 - Japanese
 - Spanish
 - Ukrainian
 - Vietnamese
Update files for v1.7.5 release.
Update docs/Release.txt.
Set MPC_NIGHTLY_RELEASE to 1.
Readme.md: switch to SVG badge.
StatusLabel: flickerless paint
PlaylistBar: drag and drop deeply nested folders

Support it.
Discard .ini cache when it's not being accessed

Refs #4193
Flush .ini cache after idle processing is done
Use the right prefix for bool variable
Construct CAppSettings in InitInstance()

It allows us to use COM objects in CAppSettings ctor.
FileAssoc: don't use static methods
FileAssoc: don't use static variables
Reduce header dependencies
Cosmetics

Placed 'extern' functions together.
Marked local functions as 'static'.
And some minor clean-ups and cosmetics.
Use 'override' keyword
A bit more sane hooks declaration
Simplify setting heap information