Prevent copyfile from failing when on Linux

plot2svg copied files in multiple occassions using MATLAB's builtin
copyfile. The latter produces an error when trying to copy a file
that is owned by a user different from that performing the copy.
A detailed explanation of this issue can be found here:

http://www.mathworks.nl/support/solutions/en/data/1-98H2VH/index.html?product=SL&solution=1-98H2VH

This issue has been solved by overriding MATLAB's built-in with
plot2svg.copyfile