Fix: MPC-HC did not start when using the INI file.

574c87b9f9affaae2d971c53f61b3fa803c18652 introduced an infinite-loop when writing the INI file. Registry storage was unaffected.

Fixes #4330.
Testing: Don't force any background color for the Shockwave graph.
Why "C:\tmp.srt"?
Fix some CPPCheck warnings or mark them as intentional.
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...
Fix: x86 and x64 versions conflicted over file associations.

4f465cf8b81f1da800b1bfc57cc48e317d24fbb5 was incomplete for Vista+.

This commit fixes #4064.