* gnu/system/uuid.scm (uuid=?): New procedure.
* tests/uuid.scm ("uuid=?"): New test.
* gnu/build/file-systems.scm (partition-uuid-predicate)
(luks-partition-uuid-predicate): Use it instead of 'bytevector=?'.
* gnu/system/uuid.scm (%fat32-uuid-rx): New variable.
(string->fat32-uuid): New procedure.
(%uuid-parsers): Add it.
* tests/uuid.scm ("uuid, FAT32, format preserved"): New test.