Boxplot correction for tikz export

Workaround for boxplots in combination with matlab2tikz(). As reported,
matlab2tikz fails to export boxplots correctly, mostly due to the quite
'special' implementation of boxplot() itself. The error "dimension too
large" will occur when compiling an automatically exported boxplot in
Latex due to a wrong positioning of the X-Tick-Labels. This short code
provides a solution through erasing the old labels and setting new ones
with correct positions.
Execute this before running matlab2tikz()...