ajaxlib/require_js: MDL-16693 $PAGE->requires->... deprecates require_js etc.

There is a new implementation of require_js in lib/deprecatedlib.php,
based on $PAGE->requires.

There were a few other recently introduced functions in lib/weblib.php,
namely print_js_call, print_delayed_js_call, print_js_config and
standard_js_config. These have been removed, since they were never in
a stable branch, and all the places that used them have been changed
to use the newer $PAGE->requires->... methods.

get_require_js_code is also gone, and the evil places that were calling
it, even though it is an internal function, have been fixed.

Also, I made some minor improvements to the code I committed yesterday
for MDL-16695.

All that remains is to update all the places in core code that are
still using require_js.

(This commit also fixes the problem where the admin tree would not
start with the right categories expanded.)

lib/filelib.php

@@ -1874,7 +1874,7 @@ function file_modify_html_header($text) {
     $ufo = '';
     if (filter_is_enabled('filter/mediaplugin')) {
         // this script is needed by most media filter plugins.
-        $ufo = get_require_js_code(array($CFG->wwwroot . '/lib/ufo.js'));
+        $ufo = ajax_get_link_to_script($CFG->wwwroot . '/lib/ufo.js');
     }
 
     preg_match('/\<head\>|\<HEAD\>/', $text, $matches);