support for __cxa_atexit argument

src/library.js

@@ -514,8 +514,8 @@ var Library = {
     throw 'exit(' + status + ') called, at ' + new Error().stack;
   },
 
-  atexit: function(func) {
-    __ATEXIT__.push(func);
+  atexit: function(func, arg) {
+    __ATEXIT__.push({ func: func, arg: arg });
   },
   __cxa_atexit: 'atexit',
 

src/preamble.js

@@ -287,11 +287,12 @@ function __initializeRuntime__() {
 
 function __shutdownRuntime__() {
   while( __ATEXIT__.length > 0) {
-    var func = __ATEXIT__.pop();
+    var atexit = __ATEXIT__.pop();
+    var func = atexit.func;
     if (typeof func === 'number') {
       func = FUNCTION_TABLE[func];
     }
-    func();
+    func(atexit.arg);
   }
 }