parse_bbc

Parse bulletin board code in a string, as well as smileys optionally. - only parses bbc tags which are not disabled in disabledBBC. - handles basic HTML, if enablePostHTML is on. - caches the from/to replace regular expressions so as not to reload them every time a string is parsed. - only parses smileys if smileys is true. - does nothing if the enableBBC setting is off. - uses the cache_id as a unique identifier to facilitate any caching it may do. - returns the modified message.