Replace non-free XML parser with libxml2

This is based on patches from Christophe Fergeau to get rid of the AFPL licensed
XML parser in libmusicbrainz (LMB-34).

Signed-off-by: Sebastian Ramacher <sramacher@debian.org>
libxml doesn't like too many hyphens

Signed-off-by: Sebastian Ramacher <sramacher@debian.org>
Add FindLibXml2 similar to FindNeon and FindJansson

Signed-off-by: Sebastian Ramacher <sramacher@debian.org>
Replace libmusicbrainz with libcoverart

Forgot to replace these two occurrences.

Signed-off-by: Sebastian Ramacher <sramacher@debian.org>
Ignore cross compilation file
Merge branch 'libxml' of https://github.com/sebastinas/libcoverart