[#33880] Protostar template now shows top 3px in background colour.

See http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33880&start=0.
(Observe the top 3 pixels of any Joomla page with Protostar template. Make sure background colour differs from
template colour to see the difference before/after fix.)