Renamed the pnacl version of atomicops.h into C11 atomic, and flagged the mac version to that if atomic is enabled

src/google/protobuf/stubs/atomicops.h

@@ -196,7 +196,11 @@ Atomic64 Release_Load(volatile const Atomic64* ptr);
 
 // Apple.
 #elif defined(GOOGLE_PROTOBUF_OS_APPLE)
+#if __has_feature(cxx_atomic) || _GNUC_VER >= 407
+#include <google/protobuf/stubs/atomicops_internals_generic_c11_atomic.h>
+#else  // __has_feature(cxx_atomic) || _GNUC_VER >= 407
 #include <google/protobuf/stubs/atomicops_internals_macosx.h>
+#endif  // __has_feature(cxx_atomic) || _GNUC_VER >= 407
 
 // GCC.
 #elif defined(__GNUC__)
@@ -217,7 +221,7 @@ Atomic64 Release_Load(volatile const Atomic64* ptr);
 #elif defined(GOOGLE_PROTOBUF_ARCH_POWER)
 #include <google/protobuf/stubs/atomicops_internals_power.h>
 #elif defined(__native_client__)
-#include <google/protobuf/stubs/atomicops_internals_pnacl.h>
+#include <google/protobuf/stubs/atomicops_internals_generic_c11_atomic.h>
 #elif defined(GOOGLE_PROTOBUF_ARCH_PPC)
 #include <google/protobuf/stubs/atomicops_internals_ppc_gcc.h>
 #elif (((__GNUC__ == 4) && (__GNUC_MINOR__ >= 7)) || (__GNUC__ > 4))

src/google/protobuf/stubs/atomicops_internals_generic_c11_atomic.h

@@ -30,8 +30,8 @@
 
 // This file is an internal atomic implementation, use atomicops.h instead.
 
-#ifndef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_PNACL_H_
-#define GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_PNACL_H_
+#ifndef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_GENERIC_C11_ATOMIC_H_
+#define GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_GENERIC_C11_ATOMIC_H_
 
 #include <atomic>
 
@@ -228,4 +228,4 @@ inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
 }  // namespace protobuf
 }  // namespace google
 
-#endif  // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_PNACL_H_
+#endif  // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_GENERIC_C11_ATOMIC_H_