Add several missing MYSQLI_ constants

All values current as of PHP 5.5.4.

I also found two other constants  [on php.net](http://php.net/manual/en/mysqli.constants.php "Mysql - predefined constants") (MYSQLI_CLIENT_MULTI_QUERIES & MYSQLI_NEED_DATA), but outside of that mention I can't find them...they're not in the 5.5.4 or master source, and I can't find any supporting documentation for them (or that they've been deprecated/removed).