NODE_DEBUG=timer instead of bitflags

lib/timers.js

@@ -1,12 +1,8 @@
 var Timer = process.binding('timer').Timer;
 var assert = process.assert;
 
-/*
- * To enable debug statements for the timers do NODE_DEBUG=8 ./node script.js
- */
-var debugLevel = parseInt(process.env.NODE_DEBUG, 16);
 var debug;
-if (debugLevel & 0x8) {
+if (process.env.NODE_debug && /timer/.test(process.env.NODE_debug)) {
   debug = function() { require('util').error.apply(this, arguments); };
 } else {
   debug = function() { };
@@ -117,9 +113,9 @@ var unenroll = exports.unenroll = function(item) {
 
     var list = lists[item._idleTimeout];
     // if empty then stop the watcher
-    //debug('unenroll');
+    debug('unenroll');
     if (list && list._idlePrev == list) {
-      //debug('unenroll: list empty');
+      debug('unenroll: list empty');
       list.stop();
     }
   }