simulate mysql_real_escape_string when not yet connected to DB

[scottconnerly]

Currently wpdb::_real_escape() falls back to addslashes() when you're not yet connected to the database

Instead, have it fall back to a closer mimic of mysql_real_escape_string():

Use this to make patch:
​http://pastebin.com/5vMaBhQe

Reference:
​http://dev.mysql.com/doc/refman/5.0/en/mysql-real-escape-string.html
​http://www.php.net/manual/en/function.mysql-real-escape-string.php

[kurtpayne]

Better replacement for mysql_real_escape_string

[kurtpayne]

This seems like a good idea. wpdb::weak_escape is already present as a wrapper to addslashes.

[kurtpayne]

Unit test for mysql_real_scape_string and fallback logic

[nacin]

We're actually always connected to the DB, so this is invalid. See also [24712].