FIX: EventEmitter#removeListener logic

In the case of one defined listener, the function should only remove it
if it is the same as the passed listener.

lib/events.js

@@ -90,7 +90,7 @@ process.EventEmitter.prototype.removeListener = function (type, listener) {
     var i = list.indexOf(listener);
     if (i < 0) return this;
     list.splice(i, 1);
-  } else {
+  } else if (this._events[type] === listener) {
     this._events[type] = null;
   }
 

test/simple/test-event-emitter-remove-listeners.js

@@ -0,0 +1,39 @@
+require("../common");
+var events = require('events');
+
+
+count = 0;
+
+function listener1 () {
+  puts('listener1');
+  count++;
+}
+
+function listener2 () {
+  puts('listener2');
+  count++;
+}
+
+function listener3 () {
+  puts('listener3');
+  count++;
+}
+
+e1 = new events.EventEmitter();
+e1.addListener("hello", listener1);
+e1.removeListener("hello", listener1);
+assert.deepEqual([], e1.listeners('hello'));
+
+e2 = new events.EventEmitter();
+e2.addListener("hello", listener1);
+e2.removeListener("hello", listener2);
+assert.deepEqual([listener1], e2.listeners('hello'));
+
+e3 = new events.EventEmitter();
+e3.addListener("hello", listener1);
+e3.addListener("hello", listener2);
+e3.removeListener("hello", listener1);
+assert.deepEqual([listener2], e3.listeners('hello'));
+
+
+