Replaced legacy mysql real_escape_string

The import currently uses the the non-MySQLi `mysql_real_escape_string`, which sometimes causes issues. Specifically, I got the error "Can't connect to local MySQL server through socket '/No-MySQL-hostname-was-specified' (2), in spite of actually being connected to the database.

I'm not sure how widespread this problem is, but I noticed a few users complaining in forums. I've switched to the newer MySQLi `real_escape_string`, which is the preferred way of doing this.