mysql-connector-c 6.1.3

Update to latest version. In order to get this lib to build on Mavericks,
I had to use the workaround documented here http://bugs.mysql.com/bug.php?id=70751

mysql-connector-c: v 6.1.3 compiles with libc++

Closes #25262.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>