Fixed the call to by the PyMOL cartoon function to the function 'file_root()' of 'io.py'.
This fixes a bug whereby the function 'io.file_root()' was being called yet it didn't exist. The
change which introduced the problem was announced at
https://mail.gna.org/public/relax-devel/2006-10/msg00228.html (Message-id:
<1162314647.3525.182.camel@...>). The fix was to call 'self.relax.IO.file_root()'.
