Rename uses of _ and __ because these are getting stepped on by macros from other system code.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@167038 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__config b/include/__config
index 75b2206..4e69964 100644
--- a/include/__config
+++ b/include/__config
@@ -415,11 +415,11 @@
 #endif
 
 #ifdef _LIBCPP_HAS_NO_STRONG_ENUMS
-#define _LIBCPP_DECLARE_STRONG_ENUM(x) struct _LIBCPP_VISIBLE x { enum _
+#define _LIBCPP_DECLARE_STRONG_ENUM(x) struct _LIBCPP_VISIBLE x { enum __lx
 #define _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(x) \
-    _ __v_; \
-    _LIBCPP_ALWAYS_INLINE x(_ __v) : __v_(__v) {} \
-    _LIBCPP_ALWAYS_INLINE explicit x(int __v) : __v_(static_cast<_>(__v)) {} \
+    __lx __v_; \
+    _LIBCPP_ALWAYS_INLINE x(__lx __v) : __v_(__v) {} \
+    _LIBCPP_ALWAYS_INLINE explicit x(int __v) : __v_(static_cast<__lx>(__v)) {} \
     _LIBCPP_ALWAYS_INLINE operator int() const {return __v_;} \
     };
 #else  // _LIBCPP_HAS_NO_STRONG_ENUMS