fix clisp build

(presumably for clisps newer than the one I have installed.)  Patch
from lp#1374702 by Vasily Postnicov
sb-bsd-sockets: Minor, mostly cosmetic, changes
sb-bsd-sockets: Separate internet protocol sockets into inet{,4}.lisp
sb-bsd-sockets: Move protocol into new file protocol.lisp

Also extended and improved documentation strings of protocol generic
functions.
sb-bsd-sockets: New macros WITH-SOCKET-[FD-AND-]ADDRESS

Also, remove SOCKET-{CONNECT,BIND} methods for LOCAL-ABSTRACT-SOCKET
since they did the same thing as the methods for SOCKET.
sb-bsd-sockets: New macros {SOCKET,ADDRINFO}-ERROR-CASE

Put {SOCKET,ADDRINFO}-ERROR-CASE and the new helper function
INTERRUPTED-P into new file util.lisp.

Removed split.lisp containing only the unused function SPLIT.
sb-bsd-sockets: Initial addition of IPv6 support in inet6.lisp
sb-bsd-sockets: Version bump, ipv6 documentation and NEWS entry