Subresync bar: Properly lock the subtitle provider when loading.

Fixes #4505.
Subresync bar: Various cosmetics.
Subresync bar: Make the list control virtual for faster loading.

The list control is just a view for the subtitle data so there is no need to duplicate it into the list control.

This makes loading a subtitle into the Subresync bar nearly instant even for complex subtitle files which will now be order of magnitude faster to load.
Don't force any background color for the Shockwave graph.

This commit fixes #1747.
ISR: Render text subtitles relative to the video frame when in doubt.
Why "C:\tmp.srt"?
WebUI: Inform the web interface that no audio stream is available.
WebUI: Make use of new [hasaudio] info.
What the hell was intended here?!

Trying to make some sense of that code. Without much luck so far...
Fix: x86 and x64 versions conflicted over file associations.

4f465cf8b81f1da800b1bfc57cc48e317d24fbb5 was incomplete for Vista+.

This commit fixes #4064.
Auto mode for relative to.