Squashed 'libmediaart/' changes from 5167238..2f0c497

2f0c497 Release 0.4.0
3cba0bf build: Fix LIBMEDIAART_BACKEND for Qt4, should be QtGui
1c6cfd6 extract: Incorrect inverse variable check for media_art_set()

git-subtree-dir: libmediaart
git-subtree-split: 2f0c4972e536ac5735385f419db367c906a36a99
Merge commit '6301ac272bfd5ea7d1afc046090624728f5f2b2a'
[packaging] update version