The column INFORMATION_SCHEMA.INNODB_MUTEXES.NAME is not populated ever since
commit 2e814d47 applied the InnoDB changes from
MySQL 5.7.9 to MariaDB Server 10.2.2.

Since the same commit, the view is only providing information about
rw_lock_t, not any mutexes.

For now, let us convert the source code file name and line number of
the rw_lock_t creation into a name. A better option in the future might
be to store the information somewhere where it can be looked up by
mysql_pfs_key_t, and possibly to remove the CREATE_FILE and CREATE_LINE
columns.