Define our own Node entry

Chromium's V8 is using external startup snapshot file while Node does
not, so we have to use Chromium's gin for V8 initialization.

atom/app/node_main.h

@@ -0,0 +1,14 @@
+// Copyright (c) 2015 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ATOM_APP_NODE_MAIN_H_
+#define ATOM_APP_NODE_MAIN_H_
+
+namespace atom {
+
+int NodeMain(int argc, char *argv[]);
+
+}  // namespace atom
+
+#endif  // ATOM_APP_NODE_MAIN_H_