MediaInfo: Fix parsing from IAsyncReader.

 - Ensure we don't try to read unavailable data.
 - Correctly handle seek requests.
 - Don't stop the analysis too early.
MediaInfo: Don't use fastest parsing option.

Fastest parsing tends to miss some info that seems important to our users so use normal parsing speed instead.

Fixes #4730.
MediaInfo: Fix analysis of raw HEVC streams.

This patch has been upstreamed to MediaInfo so there is no need to worry about it next time MediaInfo is updated.

Fixes #4891.
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...