* src/emms-print-metadata.c: Fix crash.

Short (4 lines) contrib from Arnaud Fontaine <arnau@debian.org>.
See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=715864
also: https://vcs-git-viewer.duckcorp.org/?p=people/arnau/emms.git;a=commit;h=27825228ba9d62902b75c45b1ffee3893b22cea8
Move Jesse Weinstein's contribution to the new THANKGNU file.
* doc/emms.texinfo: Document emms-print-metadata.
* AUTHORS: Add to AUTHORS based on commit records.
* THANKGNU: Add THANKGNUs based on commit records.
* AUTHORS: Add Nick Alcock.
Use commit logs to move people between AUTHORS and THANKGNUs.
Change the way lines are killed in emms-playlist-mode.

This change was requested by Rasmus and Michael Olson.
* THANKGNU: Be a bit more thankful.
Add aif files to the recognized file types.