Fix copy ctor in numeric validators classes

wxFloatingPointValidator and wxIntegerValidator copy ctor didn't copy
the associated window, so it was lost when the validator was Clone()'d.

Fix this by correctly using wxValidator copy ctor, instead of the
default one, in the copy ctor of the common wxNumValidatorBase base
class.

include/wx/valnum.h

@@ -56,7 +56,7 @@ protected:
         m_style = style;
     }
 
-    wxNumValidatorBase(const wxNumValidatorBase& other) : wxValidator()
+    wxNumValidatorBase(const wxNumValidatorBase& other) : wxValidator(other)
     {
         m_style = other.m_style;
     }