"remaining: [time]" outputs to hint users about what to expect

#1187787 points out.

added (somewhat ugly) typecasts to build warning-free on 64bit platforms (the
result of a (char *) - (char *) cannot be stored in an int universally)

Previously this was only done for OpenSSL builds.

given prefix. Building something with gnutls without it just is too error-
prone.

build...

used the default port. He was right. I fixed the problem and added the test
cases 521, 522 and 523 to verify the fix.

libcurl didn't properly send an Expect: 100-continue header. It does now.

documentational purposes.

level stuff. The FTP server communicates with sockfilt using perl's open2().
This enables easier IPv6 support and hopefully FTP-SSL support in the future.
Added four test cases for FTP-ipv6.