Changed __config to react to all of clang's currently documented has_feature flags, and renamed _LIBCPP_MOVE to _LIBCPP_HAS_NO_RVALUE_REFERENCES to be more consistent with the rest of the libc++'s flags, and with clang's nomenclature.

llvm-svn: 113086
diff --git a/libcxx/include/mutex b/libcxx/include/mutex
index ac8ca2b..8ab9c2a 100644
--- a/libcxx/include/mutex
+++ b/libcxx/include/mutex
@@ -456,7 +456,7 @@
 {
     _F __f_;
 public:
-#ifdef _LIBCPP_MOVE
+#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     explicit __call_once_param(_F&& __f) : __f_(_STD::move(__f)) {}
 #else
     explicit __call_once_param(const _F& __f) : __f_(__f) {}