ebuild changes include:

- switch to EAPI 8 (no changes needed)
- updated/completed dependencies
  - added "desktop" USE flag to control dependencies only relevant
    for desktop applications
- doc install location is now correct package name
  - ... installed as a copy to leave original contents in /opt,
    symlinking with correct name was not possible
- xdg MIME database now gets updated for MediaExpress

qt-faststart-python requires Python 2.7 which is being removed from
Gentoo. Even if 2.7 may remain available we seem to be unable to
keep such packages on a registered overlay using the utility classes
provided by Gentoo.

In general, "faststart" is today also easily and quickly achieved
through FFMPEG (without recoding), so this tool may really no longer
be needed.

Same version is available from official Gentoo repository.

Officially only compatible with Python 2.7 up to 3.3.
Not sure if still needed - was introduced for emacs JEDI but that
appears to now ship its own version through MELPA. Not needed on
local installation.

media-libs/blackmagic-desktop-video-11.6: restrict splitdebug to avoid collisions with media-video/blackmagic-media-express

Closes #1

app-crypt/acmetool: copy from https://github.com/jmesmon/overlay/ before it was removed on May 26, 2017