Subtitle queue: Ensure the queue is invalidated after seeking.

Fixes #3691.
Subtitle queue: Check the invalidation time against the segment end time.

We could miss some subtitles which needed to be invalidated.

Fixes #3691.
PGS Subtitles: Correctly reset the parser after seeking.

Subtitles displayed just after seeking could be wrong.
PGS Subtitles: Ensure the bounding box is correct when the subtitle isn't rendered.

This could cause a black flash if a subtitle failed to render (after seeking for example).

Fixes #3691.
Cosmetic: Remove an unused function.

This was forgotten during a re-factoring long ago.
CompositionObject: Delete the assignment operator for now.

Forbid the use of direct affectation for now, it would be dangerous because of possible leaks and double frees. We could do a deep copy to be safe but it could possibly hurt the performance if we forgot about this and start using affectation a lot.
Lite builds: Fix a minor inconsistency regarding the output directory.

Lite debug builds use "mpc-hc_x??_Debug Lite" while release builds always used "mpc-hc_x??" for both normal and lite builds.
Fix: x86 and x64 versions conflicted over file associations.

4f465cf8b81f1da800b1bfc57cc48e317d24fbb5 was incomplete for Vista+.

This commit fixes #4064.
Language menu: Ensure "Language" always appears in English in menu entry.

If "Language" doesn't appear in the translated string, "(Language)" will be appended automatically.