This is the 5.8 version of the patch.

Remove the sync_frm system variable.

(cherry picked from commit 13f34489207fcf5dd5fa6058ac61aef20de1b354)

Conflicts:
	mysql-test/r/lock_multi_bug38499.result
	mysql-test/r/lock_multi_bug38691.result
	mysql-test/r/mysqld--help-notwin.result
	mysql-test/r/mysqld--help-win.result
	mysql-test/suite/sys_vars/r/sync_frm_basic.result
	sql/parse_file.cc
	sql/sys_vars.cc