Log Message:
Update libmusicbrainz5 to version 5.1.0.

Changelog:

Changes for libmusicbrainz 5.1.0
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   - Fix LMB-33 - Handle 'ended' element in 'relation'
   - Fix LMB-34 - Remove non-free XML parser and replace with libxml2
   - Add support for cross-compilation and building out of tree