Because the existing cache is global, there is no way to differentiate between
each of two databases which may be two different DBAL objects pointing to
servers with wildly different versions of an RDBMS. phpBB only has this
situation in the UCF, thus only one file changed outside the DBAL. I have
added a second optional parameter, $use_cache to each of the implementations
of dbal::sql_server_info()
PHPBB3-9637