added wxTextEntry::DoGetValue() to allow returning empty string if the control currently contains hint text

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@59265 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/textentry.h

@@ -59,6 +59,8 @@ public:
 #endif // wxUSE_UXTHEME
 
 protected:
+    virtual wxString DoGetValue() const;
+
     // this is really a hook for multiline text controls as the single line
     // ones don't need to ever scroll to show the selection but having it here
     // allows us to put Remove() in the base class