OTHER: Remove unused volume button class.
OTHER: Make playback label clickable for search.
OTHER: Remove unused declarations.
OTHER: Unbreak entry_changed signal handler for playlist model.
OTHER: Just say 'Abraca' in playback label before playback starts.
OTHER: Silence incompatible pointer type warning.
OTHER: Rename AbracaMainWindow -> AbracaWindow.
OTHER: Handle missing volume channels better.

Volume channels may come and go during xmms2d lifetime.
When playback starts we perform an additional query to
make life easier for users of the volume API.
OTHER: Avoid deprecated APIs.
OTHER: Add -fdiagnostics-show-option compiler option.
OTHER: Expose more xmmsv_dict_iter_t functions.
OTHER: Modernize equalizer window.
BUG(17): Unify playlist entry creation and population.

Prior to this commit, Abraca first creates cells with "insert" or "add"
and then separately populates them using "set".

Certain accessibility services intercept the insertion before anything
was stored, examining the cell content via AbracaPlaylistMode.get_value.
This triggers requesting song information from xmms2, if needed,
resulting in an erroneous request of media id 0, which leads to
seemingly empty entries in the playlist.

Accessibility tools that trigger this behaviour are for example screen
magnifiers or even gnome-shell 3.12 itself, as long as it is not built
including the patch to initialize at-spi on demand
<https://bugzilla.gnome.org/show_bug.cgi?id=730118>.

This commit unifies insertion and population to a single call to
"insert_with_values", making interception impossible in between.
OTHER: Add Dominik Fischer to AUTHORS.
OTHER: Add forgotten .ui file for equalizer.
OTHER: Change playback icons to symbolic ones.

Thanks to gnome-music for the inspiration.
OTHER: Make AUTHORS match about dialog.
OTHER: Add build dir to gresources search path.
OTHER: Add a waf AUTHORS parser/transformer tool.
OTHER: Transform about ui description into template.