[AArch64] Add support for __builtin_ms_va_list on aarch64

Move builtins from the x86 specific scope into the global
scope. Their use is still limited to x86_64 and aarch64 though.

This allows wine on aarch64 to properly handle variadic functions.

Differential Revision: https://reviews.llvm.org/D34475

llvm-svn: 308218
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index dc25e52..4e7c6c4 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2529,7 +2529,7 @@
   case CC_X86ThisCall:
   case CC_X86VectorCall:
   case CC_X86Pascal:
-  case CC_X86_64Win64:
+  case CC_Win64:
   case CC_X86_64SysV:
   case CC_X86RegCall:
   case CC_AAPCS: