Ticket #2807: incomplete sand256 skin.

When using the sand256 skin, selected element is not highlighted in
pop-up menus.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

misc/skins/sand256.ini

@@ -131,6 +131,11 @@
     menuhotsel=;rgb551;underline
     menuinactive=
 
+[popupmenu]
+    _default_=black;rgb553 
+    menusel=;rgb452;underline
+    menutitle=;;underline
+
 [buttonbar]
     hotkey=black;rgb554
     button=black;rgb452