Make mojo_system static and mojo_system_impl a component, never use both

mojo/system/entrypoints.h

Index: mojo/system/entrypoints.h
diff --git a/mojo/system/entrypoints.h b/mojo/system/entrypoints.h
new file mode 100644
index 0000000000000000000000000000000000000000..65a03631e6a5867712f5382bb41dd46c9905ec23
--- /dev/null
+++ b/mojo/system/entrypoints.h
@@ -0,0 +1,24 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_SYSTEM_ENTRYPOINTS_H
+#define MOJO_SYSTEM_ENTRYPOINTS_H
+
+namespace mojo {
+namespace system {
+
+class Core;
+
+namespace entrypoints {
+
+// Sets the instance of Core to be used by system functions.
+void SetCore(Core* core);
+// Gets the instance of Core to be used by system functions.
+Core* GetCore();
+
+}  // namespace entrypoints
+}  // namepace system
+}  // namespace mojo
+
+#endif  // MOJO_SYSTEM_ENTRYPOINTS_H