From MariaDB 10.3.5, the saved binlog position is stored in multiple
entries in each rseg header, and during recovery the most recent of
them is selected as the postion to recover. The comparison between
different entries is by comparing the binlog file name and offset.
This fails if the binlog file name changes to something that compares
smaller, which can happen from RESET MASTER (which goes back to the
suffix .000001) or from renaming the basename of the binlog. As a
result, the wrong position can be recovered after RESET MASTER or
binlog rename.

This commit writes an 8-byte incrementing version number with each
position entry. The version is allocated during
innobase_commit_ordered(), which ensures that a higher version number
will correspond to a more recent commit. The recovered position is
then the entry with the highest version number.

If starting on a database written by earlier server version, the code
falls back to the old methods of comparing position entries.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>