Migrating from usrp2 to uhd

I had some old usrp2 dependencies lying around my code which of course
broke when I did a fresh git. Other than removing any obvious usrp2
calls, I also changed all instances of uhd::usrp::single_usrp to
uhd::usrp::multi_usrp. This seems to work, but is it the correct thing
to do? Was single_usrp removed completed or just moved to a different
location?

Also, my code seems to work but I’m getting a lot of “L’s” being printed
to stdout, similar to O’s and U’s for overruns and underruns,
respectively. I didn’t see anything on the Ettus website explaining the
the L means.