Use ${datarootdir} instead of ${datadir} for data files that go
in directories which are shared with other apps. In practical
terms, this doesn't change anything for most users since
${datarootdir} and ${datadir} are the same by default. But this
is useful for distros/OSes which like to store the application
specific files somewhere else then at the root of /usr/share.
Changes to allow this in audacious-plugins will follow.

	modified:   Makefile
	modified:   configure.ac
	modified:   pixmaps/Makefile
	modified:   src/audacious/Makefile
In my previous commit to allow the use of the --with-pkgconfigdir
switch, I inadvertently forgot to update the uninstall target.

	modified:   Makefile
Optionally install a support file for Xfce's Thunar file manager.
This adds an entry in Thunar's context menus to send files and
directories to the Audacious playlist. This is disabled by
default.

	modified:   Makefile
	modified:   configure.ac
	new file:   contrib/Makefile
	new file:   contrib/thunar-sendto-audacious-playlist.desktop
	modified:   extra.mk.in
Merge pull request #8 from cjsthompson/master

Fixes and enhancements.