Check for correct window in wxNumValidatorBase::SetWindow()

Override SetWindow() to check that the validator is being associated
with the window of the correct type, this allows to trigger an assert
immediately if this is not the case, making it simpler to find the error
as the call to SetValitator() on the wrong window will be in the call
stack when this happens, unlike before when the assert would happen only
at some later time.

include/wx/valnum.h

@@ -50,6 +50,10 @@ public:
     // we don't need this as we do our validation on the fly here.
     virtual bool Validate(wxWindow * WXUNUSED(parent)) wxOVERRIDE { return true; }
 
+    // Override base class method to check that the window is a text control or
+    // combobox.
+    virtual void SetWindow(wxWindow *win) wxOVERRIDE;
+
 protected:
     wxNumValidatorBase(int style)
     {