FIX "Insert Link" and other TinyMCE loading bugs (fixes #8327)

Caused by SS loading a URL with html entities (&)
through the Requirements API, which only works when directly
inserted into the HTML template (standard behaviour),
but garbles the URL GET parameters when loaded via the jQuery.ondemand
JavaScript/XHR logic.

It didn't fail the request, just meant that tiny_mce_gzip.php wasn't
getting all the required options from the GET parameters.
And since this newly loaded file contains the same JS globals,
it would override previously loaded (correct) state.

forms/HtmlEditorField.php

@@ -33,7 +33,7 @@ public static function include_js() {
 				'languages' => $configObj->getOption('language')
 			), true);
 			preg_match('/src="([^"]*)"/', $tag, $matches);
-			Requirements::javascript($matches[1]);
+			Requirements::javascript(html_entity_decode($matches[1]));
 
 		} else {
 			Requirements::javascript(MCE_ROOT . 'tiny_mce_src.js');