with the variables in the code that manipulates these values.

patch by Bardur Arantsson.

with autoconf 2.58 and above.

implements listening on multiple addresses and a fix for IPv6-only
systems.

non-root, and to ignore a gid of -1.

current file received some literal data yet or not.

f_name() returns.  Also used in a call to recv_generator() to keep the
name safe for the duration of the call.

This prevents things like the hard-link code from losing the name
before we're finished with it.

comparing two file_struct elements without copying them first, and
(2) f_name_to() which lets us supply the destination buffer for a
f_name() call (to allow it to persist without an extra copy).