TCP buttons can distinguish up and down highlight backgrounds...

... But make them nondistinct in all themes, so this commit does not yet make
user visible changes.

This uses the HiliteButtonExpandSel resource which was previously unused.
Perhaps not the intended use of the resource so named, but names can change in
2.2.1.

The two were already alike in Classic but the unused one had been just black
in the others.

src/AColor.cpp

@@ -238,7 +238,7 @@ void AColor::Bevel2
 {
    int index = 0;
    if ( bHighlight )
-      index = bmpHiliteButtonExpand;
+      index = up ? bmpHiliteButtonExpand : bmpHiliteButtonExpandSel;
    else if( bSel )
       index = up ? bmpUpButtonExpandSel : bmpDownButtonExpandSel;
    else