re PR libstdc++/49894 ([C++0x] Uniform initialization in constructor)

	PR libstdc++/49894
	PR bootstrap/50982
	* include/std/mutex (once_flag): Use NSDMI.

From-SVN: r181013

libstdc++-v3/ChangeLog

+2011-11-05  Jonathan Wakely  <jwakely.gcc@gmail.com>
+
+	PR libstdc++/49894
+	PR bootstrap/50982
+	* include/std/mutex (once_flag): Use NSDMI.
+
 2011-11-04  Benjamin Kosnik  <bkoz@redhat.com>
 
 	* scripts/run_doxygen: Fix sed quoting.

libstdc++-v3/include/std/mutex

@@ -760,11 +760,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   {
   private:
     typedef __gthread_once_t __native_type;
-    __native_type  _M_once;
+    __native_type  _M_once = __GTHREAD_ONCE_INIT;
 
   public:
     /// Constructor
-    constexpr once_flag() noexcept : _M_once(__GTHREAD_ONCE_INIT) { }
+    constexpr once_flag() noexcept = default;
 
     /// Deleted copy constructor
     once_flag(const once_flag&) = delete;