Mojo: Move public C system header files to mojo/public/c/system/.

mojo/public/c/system/macros.h

 // Copyright 2013 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_PUBLIC_SYSTEM_MACROS_H_
-#define MOJO_PUBLIC_SYSTEM_MACROS_H_
+#ifndef MOJO_PUBLIC_C_SYSTEM_MACROS_H_
+#define MOJO_PUBLIC_C_SYSTEM_MACROS_H_
 
 #include <stddef.h>
 
 // Annotate a variable indicating it's okay if it's unused.
 // Use like:
 //   int x MOJO_ALLOW_UNUSED = ...;
 #if defined(__GNUC__)
 #define MOJO_ALLOW_UNUSED __attribute__((unused))
 #else
 #define MOJO_ALLOW_UNUSED
@@ skipping 56 matching lines @@
   type(type&); \
   void operator=(type&); \
  public: \
   operator rvalue_type() { return rvalue_type(this); } \
   type Pass() { return type(rvalue_type(this)); } \
   typedef void MoveOnlyTypeForCPP03; \
  private:
 
 #endif  // __cplusplus
 
-#endif  // MOJO_PUBLIC_SYSTEM_MACROS_H_
+#endif  // MOJO_PUBLIC_C_SYSTEM_MACROS_H_