Optimize get-peer/local-address-and-port.

Instead of calling USOCKET:GET-X-ADDRESS and USOCKET:GET-X-PORT
separately, call GET-X-NAME, which returns address and port as two
values. At least for SBCL GET-X-ADDRESS and GET-X-PORT are implemented
as NTH-VALUE 0/1 of GET-X-NAME, which causes the address to be consed
twice.