#i125020# fix rounding error in AquaSalGraphics::RefreshRect()

Rounding left and width down can accumulate a rounding error of almost two in
the calculation of right. The existing code compensates for this by increasing
the width by two, but since left has been decremented by one to accommodate for
antialiasing artifacts this compensation is one to few by itself and two to few
when accounting for antialiasing artifacts on the right. Y-pos and height have
the same problems and get the matching fix.

(cherry picked from commit 073ec69fb970830d39c8700317ee74dbbdfd1fda)