Feature Release 05

A quick new release to fix a semi-urgent bug, but there are also a few other additions:

• Also enable stereo playback for the various Linux audio players. After merging the audio system rework in the last release, all available audio players can now play multi-channel audio.
• Add "Copy subtitles to clipboard" and "Save subtitles as PNG" options to the right-click menu on the video display. This will copy only the subtitles with a transparent background.
• Fix some file permission checks on Windows (or, rather, remove unnecessary ones). In particular, this will fix some usages of the Font Collector, such as when copying fonts to a folder in a Samba mount.
• Fix an assertion error when loading the waveform audio display. This crept in after merging the audio system rework in the last release, and went unnoticed for a surprisingly long time - probably because nobody actually uses the waveform display.

The additional audio/video sources have been disabled on the macOS builds for now. BestSource doesn't compile due to an upstream error, and Avisynth/VapourSynth would first need to be ported to macOS.