Fix a crash when the maximum number of recent files is set to 0.

We inherited a bug from Microsoft's CRecentFileList which claimed to support a size of 0 but unconditionally access the element 0 of the list.
Fullscreen option page: Automatically resize the list control on init.

Fixes #4653.
Comment out some unused variable assignments.

Those can be useful if the functions are extended one day.
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...