Add an interface for channel list and change to the web server.

This change adds a JSON interface for obtaining the list of channels
currently available via the DVB interface in MPC-HC, and a simple facility
which allows the client to change the currently played channel.
CAppSettings: Remove the copy constructor and assignment operator.

We don't want to accidentally copy the settings.

Also don't mark the constructor as virtual.
Don't warn the user when some DVD hooks fail.

Those hooks aren't critical for DVD playback and they often fail due to an incompatibility with NVIDIA drivers on some systems which unfortunately we can't fix on our side.

Refs: #3739.
VSFilter: Be more careful when using IMediaSample2 interface.
Sync Renderer: Remove some unneeded casts.
Update translations from Transifex:

 - Basque
 - Catalan
 - Chinese (simplified and traditional)
 - French
 - German
 - Greek
 - Hungarian
 - Japanese
 - Polish
 - Slovak
 - Turkish
 - Ukrainian
Add an option to prevent creating the external style file when saving a subtitle.
Updated LAV Filters to 0.61.2-40-42f583f (custom build based on 0.61.2-35-6c73517)

Important change:
 - LAV Video: Fix some issues with DVD subtitles (flashing, overlapping and generally all kind of timing issues) (fixes #4032).
Cosmetic changes.

* use `nullptr` instead of `0` when it makes sense
* follow the same scheme when declaring variables
Re-indent file.
Remove unused code (`MakeAACInitData`).
Fix standalone filters compilation after 58df3305748f32017f7d72bda69388e13afbc9cd.
CoordGeom: Improve const correctness.

Also mark constant as float when it makes sense.
Subpic interfaces: Improve the const correctness.

The ABI isn't modified but the interfaces are for internal use anyway.
SubPicImpl: Minor cosmetics.
DX7 Subpic: Avoid resetting the static subpicture when possible.

Also use safer locking.
DX9 Subpic: Avoid resetting the static subpic and the subpic pool when possible.

Also use safer locking.
DX9 Subpic: Remove unused code.
Memory subpic: Mark some global variables static and minor cosmetics.
SubPicAllocators: Const correctness and minor cosmetics.