add more pure virtuals to wxBrushBase; fix the GetColour() functions to return a wxColour object and not a reference; remove from docs the non-existent SetColour(const wxString&) overloads

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52901 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/pen.cpp

@@ -230,7 +230,7 @@ int wxPen::GetWidth() const
     return M_PENDATA->m_width;
 }
 
-wxColour &wxPen::GetColour() const
+wxColour wxPen::GetColour() const
 {
     wxCHECK_MSG( Ok(), wxNullColour, wxT("invalid pen") );