Merge MySQL 5.7.12

https://github.com/percona/percona-server/pull/542

Merge MySQL 5.7.12.

Review http://jenkins.percona.com/job/mysql-5.7-param/138/#showFailuresLink results, innodb.innodb_file_limit_check could be a testcase bug that needs reporting

Verify and revert our fix for https://bugs.mysql.com/79117
Re-enable command line super_read_only testcases (https://bugs.mysql.com/79328)
Verify and revert upstream fix for https://bugs.launchpad.net/percona-server/+bug/1475107 / http://bugs.mysql.com/bug.php?id=77684, keep our testcase if necessary

Add a testcase for 74578, 73556 / bug 1354011 (missed in 5.7.10)

Verify the fix for https://bugs.mysql.com/bug.php?id=79236

Verify the fix for https://bugs.mysql.com/bug.php?id=78963 by re-enabling rpl.rpl_ignore_super_read_only, and keeping or removing the testcase depending on the upstream fix test coverage

Verify the fix for https://bugs.mysql.com/bug.php?id=78223 by re-enabling for Valgrind binlog/t/binlog_mysqlbinlog_start_stop, rpl/t/rpl_row_mysqlbinlog, t/mysqlbinlog.test, and t/mysqlbinlog_raw_mode tests. Check ASan test status.