Fix: The tracks could be duplicated in the "Details" tab of the "Properties" dialog.

One line got lost in 072b1f04d3cad6f0a5f29d48f91aa47da307e062.

Fixes #5029.
DSUtil: Remove duplicated function "FileExists".
Cosmetics: Remove unused include.
DSUtil: Remove duplicated function GetProgramPath.
Cosmetics: Use PathUtils::GetProgramPath when possible.
VSFilter: Remove an unused function.
Cosmetics: External toolbar image: Replace nested if by loops.
AStyle: Increase max-instatement-indent from 40 to 50.
120
Don't force any background color for the Shockwave graph.

This commit fixes #1747.
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...