[R-sig-Debian] cran ubuntu repository and ubuntu 12.10

[Chris Sims]

Since upgrading to quantal, I find that synaptic and apt-get cannot read 
the sources.list file if it includes the previously standard line

deb http://lib.stat.cmu.edu/R/CRAN/bin/linux/ubuntu/ quantal

This line makes apt-get or synaptic give an error message identifying 
this line as having a syntax error.

If "multiverse" is added at the end of the line, the line is parsed, but 
then apt-get or synaptic looks for non-existent directories on the server.