Specialize std::hash<> for wxString when using C++11.

This allows to use wxString as key type of std::unordered_{map,hash} out of
the box.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77518 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -43,6 +43,7 @@ All:
 - Define wxOVERRIDE as override for supporting compilers (Thomas Goyne).
 - Allow specifying custom comparator for wxSortedArrayString (Catalin Raceanu).
 - Add wxDateTime::GetWeekBasedYear().
+- Specialize std::hash<> for wxString when using C++11.
 
 Unix:
 

include/wx/string.h

@@ -3915,6 +3915,28 @@ wxDEFINE_ALL_COMPARISONS(const char *, const wxCStrData&, wxCMP_CHAR_CSTRDATA)
 #undef wxCMP_CHAR_CSTRDATA
 #undef wxCMP_WCHAR_CSTRDATA
 
+// ----------------------------------------------------------------------------
+// Implement hashing using C++11 std::hash<>.
+// ----------------------------------------------------------------------------
+
+#if __cplusplus >= 201103L || wxCHECK_VISUALC_VERSION(10)
+
+#include <functional>
+
+namespace std
+{
+    template<>
+    struct hash<wxString>
+    {
+        size_t operator()(const wxString& s) const
+        {
+            return std::hash<std::wstring>()(s.ToStdWstring());
+        }
+    };
+} // namespace std
+
+#endif // C++11
+
 // ---------------------------------------------------------------------------
 // Implementation only from here until the end of file
 // ---------------------------------------------------------------------------