Revert "Add a work around for clang 2.9"

This reverts commit 26a7908.

vm/util/atomic.hpp

@@ -219,53 +219,6 @@ namespace atomic {
 #endif
   }
 
-// This is a very dirty work around for a bug in Clang 2.9 (or Apple clang 2.0)
-// The bug is that it can't correctly instantiate templates when used with
-// built-in functions for atomic memory access (a GCC extension). It is fixed
-// in Clang 3.0 or later.
-//
-// To work around, we define all explicit template specializations needed by
-// current Rubinius code.
-//
-// The error:
-//   vm/util/atomic.hpp:185:33: error:
-//     cannot initialize a parameter of type 'volatile long long *' with
-//     an lvalue of type 'int *'
-//       return __sync_fetch_and_sub(ptr, inc);
-//                                   ^~~
-//   In file included from vm/shared_state.cpp:18:
-//   vm/world_state.hpp:64:9: note:
-//     in instantiation of function template specialization
-//     'atomic::fetch_and_sub<int>' requested here
-//       atomic::fetch_and_sub(&pending_threads_, 1);
-//       ^
-//
-// The bug report:
-//   http://llvm.org/bugs/show_bug.cgi?id=8345 and
-// The fix:
-//   https://llvm.org/viewvc/llvm-project?view=rev&sortby=date&revision=139373
-#if defined(__clang__) && ( \
-      ((__clang_major__ == 2) && (__clang_minor__ == 9)) || \
-      ((__clang_major__ == 2) && (__clang_minor__ == 0)))
-  // For WorldState::pending_threads_
-  template <> inline int fetch_and_add(int *ptr, int inc) {
-    return __sync_fetch_and_add(ptr, inc);
-  }
-
-  template <> inline int fetch_and_sub(int* ptr, int inc) {
-    return __sync_fetch_and_sub(ptr, inc);
-  }
-
-  // For ObjectMemory::last_object_id
-  template <> inline size_t fetch_and_add(size_t *ptr, size_t inc) {
-    return __sync_fetch_and_add(ptr, inc);
-  }
-
-  template <> inline size_t fetch_and_sub(size_t* ptr, size_t inc) {
-    return __sync_fetch_and_sub(ptr, inc);
-  }
-#endif
-
   template <typename T> inline T read(T *ptr) {
     memory_barrier();
     return *ptr;