$db_type not in global scope, making updates fail

adrian's "support for multiple database connections" patch from 2004/04/30 moves

  $db_type = substr($db_url, 0, strpos($db_url, "://"));

out of the global scope, which makes it unavailable for updates.inc, which causes updates to fail because postgresql sql is executed for mysql databases (and the other way round). the obvisous fix is to declare $db_type global:

   function db_set_active($name = 'default') {
-    global $db_url;
-    global $active_db;
+    global $db_url, $db_type, $active_db;
     static $db_conns;