as error (*). This occurs typically when signal is received.
(*) For older version, we already deal with short read(2) from remote
host in sink(). But for other cases, i.e., write(2) to local file in
sink(), read(2)/write(2) in source(), error was raised.
This version of rcp(1) can successfully send/receive files with older
version, even if short read(2)/write(2) occurs by SIGINFO.
Also, when real error occurs, give up immediately instead of continue to
send/receive wrong data.
Clean up the mess a little bit as well...
2316fa6ff0