process: ensure that "exit" doesn't get emitted twice on a natural exit

Fixes "test/simple/test-process-exit.js".

src/node.cc

@@ -2772,6 +2772,7 @@ char** Init(int argc, char *argv[]) {
 
 void EmitExit(v8::Handle<v8::Object> process_l) {
   // process.emit('exit')
+  process_l->Set(String::NewSymbol("_exiting"), True());
   Local<Value> emit_v = process_l->Get(String::New("emit"));
   assert(emit_v->IsFunction());
   Local<Function> emit = Local<Function>::Cast(emit_v);

src/node.js

@@ -409,11 +409,9 @@
   };
 
   startup.processKillAndExit = function() {
-    var exiting = false;
-
     process.exit = function(code) {
-      if (!exiting) {
-        exiting = true;
+      if (!process._exiting) {
+        process._exiting = true;
         process.emit('exit', code || 0);
       }
       process.reallyExit(code || 0);