Fix setting colours for the edit control part of wxComboBox.

Recognize this control as part of wxComboBox and so handle WM_CTLCOLOR for it.

To do this, override ContainsHWND() in wxComboBox and use it, on the parent
window, in wxControl::DoMSWControlColor(), if we fail to find the window
directly.

Closes #811.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72468 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/combobox.cpp

@@ -550,6 +550,11 @@ void wxComboBox::Clear()
         wxTextEntry::Clear();
 }
 
+bool wxComboBox::ContainsHWND(WXHWND hWnd) const
+{
+    return hWnd == GetEditHWNDIfAvailable();
+}
+
 void wxComboBox::GetSelection(long *from, long *to) const
 {
     if ( !HasFlag(wxCB_READONLY) )