rosmatlab: redirect stderr output to /dev/null in system command calls in setup.m

With Matlab R2014a and ROS hydro in Ubuntu precise I got the following error message without that patch:

>> system('rospack find rosmatlab')
rospack: /usr/local/MATLAB/R2014a/bin/glnxa64/libcrypto.so.1.0.0: no version information available (required by /usr/lib/libpython2.7.so.1.0)
rospack: /usr/local/MATLAB/R2014a/bin/glnxa64/libssl.so.1.0.0: no version information available (required by /usr/lib/libpython2.7.so.1.0)
/usr/local/MATLAB/R2014a/ros/hydro/share/rosmatlab

ans =

     0

>>