Updated LAV Filters to 0.62-33-9dfd943 (custom build based on 0.62-28-bce3ebe).

Important changes:
 - LAV Splitter: improved GIF support (including animated GIF).
 - Updated ffmpeg library.
Formats option page: Reworked UI.

Replace the text buttons by icon buttons and add a new button to clear all associations.

Also replace the "with icons" checkbox text with something clearer now that there is more space.

Fixes #4687.
Don't force any background color for the Shockwave graph.

This commit fixes #1747.
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...