Fixed: clearTimeouts calling multiple times

When clearTimeouts was called on a timer multiple times, it would break the
doubly-linked list along with future timeouts. This patch fixes that.

lib/timers.js

@@ -43,6 +43,7 @@ function shift (list) {
 function remove (item) {
   item._idleNext._idlePrev = item._idlePrev;
   item._idlePrev._idleNext = item._idleNext;
+  item._idleNext = null;
 }
 
 
@@ -111,8 +112,7 @@ function insert (item, msecs) {
 
 var unenroll = exports.unenroll = function (item) {
   if (item._idleNext) {
-    item._idleNext._idlePrev = item._idlePrev;
-    item._idlePrev._idleNext = item._idleNext;
+    remove(item);
 
     var list = lists[item._idleTimeout];
     // if empty then stop the watcher

test/pummel/test-timers.js

@@ -84,8 +84,26 @@ interval4 = setInterval(function () {
   if (++count4 > 10) clearInterval(interval4);
 }, 0);
 
+
+// we should be able to clearTimeout multiple times without breakage.
+var expectedTimeouts = 3;
+
+function t () {
+  expectedTimeouts--;
+}
+
+w = setTimeout(t, 200),
+x = setTimeout(t, 200),
+y = setTimeout(t, 200);
+
+clearTimeout(y),
+z = setTimeout(t, 200);
+clearTimeout(y);
+
+
 process.addListener("exit", function () {
   assert.equal(true, setTimeout_called);
   assert.equal(3, interval_count);
   assert.equal(11, count4);
+  assert.equal(0, expectedTimeouts, "clearTimeout cleared too many timeouts");
 });