sb-bsd-sockets: Fix type of canonname in addrinfo.

Should be c-string-pointer, not c-string.

Fixes lp#1187041, patch by Jerry James.
Uninitialized type-error conditions can now be printed.

(print (make-condition 'simple-type-error)) signalled an unbound slot
error.

Reported by Eric Marsden, fixes lp#1184586.
Simpler and more precise type derivation for APPEND/NCONC

 We can suppose that all but the last argument are lists when
 deriving the return type... and the logic to compute the return
 type can be much simpler: it's either a CONS, the last argument,
 or we don't know which (yet).