Since bug@20166, which replaced the binlog file name generating to base
on pidfile_name instead of the previous glob_hostname, the binlog file
name suddenly started to be stored solely in the absolute path format,
including a case when --log-bin option meant a relative path.
What's more serious, the path for binlog file can lead unrequestedly
to pid-file directory so that after any proper fix for this bug
there might be similar to the bug report consequences for one who
upgrades from post-fix-bug@20166-pre-fix-bug@28597 to post-fix-bug@28597.
Fixed with preserving`pidfile_name' (intr.by bug@20166) but stripping
off its directory part. This restores the original logics of storing
the names in compatible with --log-bin option format and with the
requirement for --log-bin ralative path to corresond to the data directory.
Side effects for this fix:
effective fixing bug@27070, refining its test;
ensuring no overrun for buff can happen anymore (Bug#31836
insufficient space reserved for the suffix of relay log file name);
bug#31837 --remove_file $MYSQLTEST_VARDIR/tmp/bug14157.sql missed
in rpl_temporary.test;
fixes Bug@28603 Invalid log-bin default location;
in short we now record whenever the slave I/O thread ignores a master's event because of its server id,
and use this info in the slave SQL thread to advance Exec_master_log_pos. Because if we
do not, this variable stays at the position of the last executed event, i.e. the last *non-ignored*
executed one, which may not be the last of the master's binlog (and so the slave *looks* behind
the master though it's data-wise it's not).