bool wxString::operator!() const added

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@1505 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -266,6 +266,8 @@ public:
   size_t Len() const { return GetStringData()->nDataLength; }
     // string contains any characters?
   bool IsEmpty() const { return Len() == 0; }
+    // empty string is "FALSE", so !str will return TRUE
+  bool operator!() const { return IsEmpty(); }
     // empty string contents
   void Empty()
   {