Cosmetics: reindent file.
MakeAccelShortcutLabel: Skip non-defined hotkeys.

Fixes #4876.
Subtitle delay step tooltip: Show "<not defined>" when a hotkey isn't set.
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...