[mod_authn_dbi] copy strings before escaping
[mod_authn_dbi] copy strings before escaping

dbi_conn_escape_string_copy() requires '\0'-terminated string.
While that is currently the case for strings in http_auth_info_t,
that will soon change, so consumers must use ai->username with ai->ulen,
and ai->realm with ai->rlen

gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4