make debug window draggable

prefs.js

@@ -1459,6 +1459,8 @@ function init() {
 			debug('debug mode activated');
 		}
 
+		new Draggable('debug_output');
+
 		// IE kludge
 		if (!xmlhttp) {
 			document.getElementById("prefContent").innerHTML = 

tt-rss.js

@@ -343,6 +343,8 @@ function init() {
 			debug('debug mode activated');
 		}
 
+		new Draggable('debug_output');
+
 		var params = "&ua=" + param_escape(navigator.userAgent);
 
 		loading_set_progress(30);