Revert "[libc++] Refactoring __sync_* builtins; NFC (Reland)"

This reverts commit r307595. The commit had some issues that needed
to first be addressed in review.

llvm-svn: 307746
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: e82f49849b259c9e6dd2b310fb5e46c0c2ee306a
diff --git a/src/locale.cpp b/src/locale.cpp
index e73e6d5..3b4c83a 100644
--- a/src/locale.cpp
+++ b/src/locale.cpp
@@ -28,7 +28,6 @@
 #define _CTYPE_DISABLE_MACROS
 #endif
 #include "cwctype"
-#include "__atomic_support"
 #include "__sso_allocator"
 #if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
 #include "support/win32/locale_win32.h"
@@ -668,7 +667,7 @@
 void
 locale::id::__init()
 {
-    __id_ = __libcpp_sync_add_and_fetch(&__next_id, 1);
+    __id_ = __sync_add_and_fetch(&__next_id, 1);
 }
 
 // template <> class collate_byname<char>