MDL-15748 get_user_access_sitewide() - reduce looking for perms in any context below category level.

Dramatic speed-up in sites with zillions of contexts and overrides. Credit goes to Samuli Karevaara.

lib/accesslib.php

@@ -1252,9 +1252,9 @@ function get_user_access_sitewide($userid) {
             JOIN {$CFG->prefix}role_capabilities rco
               ON (rco.roleid=ra.roleid AND rco.contextid=sctx.id)
             WHERE ra.userid = $userid
-                  AND sctx.contextlevel <= ".CONTEXT_COURSE."
+              AND ctx.contextlevel <= ".CONTEXT_COURSECAT."
+              AND sctx.contextlevel <= ".CONTEXT_COURSE."
             ORDER BY sctx.depth, sctx.path, ra.roleid";
-
     $rs = get_recordset_sql($sql);
     if ($rs) {
         while ($rd = rs_fetch_next_record($rs)) {