Howard Chu brought the bulk work of this patch that properly
moves out the sending and recving of data to the parts of the
code that are properly responsible for the various ways of doing
so.

Daniel Stenberg assisted with polishing a few bits and fixed some
minor flaws in the original patch.

Another upside of this patch is that we now abuse CURLcodes less
with the "magic" -1 return codes and instead use CURLE_AGAIN more
consistently.

This is Hoi-Ho Chan's patch with some minor fixes by me. There
are some potential issues in this, but none worse than we can
sort out on the list and over time.

... and GnuTLS connects are non-blocking, TFTP is better
integrated as a "real" protocol and RTSP is supported.

Since commit c2888604 by Jerome Vouillon

It's not quite fair to list TFTP is a "crappy" member of the
libcurl family so I removed its mentioning.

The main change is to allow input from user-specified methods,
when they are specified with CURLOPT_READFUNCTION.
All calls to fflush(stdout) in telnet.c were removed, which makes
using 'curl telnet://foo.com' painful since prompts and other data
are not always returned to the user promptly.  Use
'curl --no-buffer telnet://foo.com

' instead.  In general,
the user should have their CURLOPT_WRITEFUNCTION do a fflush
for interactive use.

Also fix assumption that reading from stdin never returns < 0.
Old code could crash in that case.

Call progress functions in telnet main loop.

Signed-off-by: Ben Greear <greearb@candelatech.com>

addressing http://curl.haxx.se/mail/lib-2009-12/0031.html

This is required in Scratchbox where
LIBTOOL=/targets/links/arch_tools/bin/libtool
is set in the environment.

The necessary libssh2 functions require libssh2 1.2.5 or later.

Make sure we don't call memcpy() if the argument is NULL even
though we also passed a zero length then, as the clang analyzer
whined and we want to limit warnings (even false positives) when
they're this easy to fix.

The change of (char) to (unsigned char) will fix long user names
and passwords on systems that have the char type signed by
default.

--proto tells curl to use the listed protocols for its initial
retrieval

--proto-redir tells curl to use the listed protocols after a
redirect

Also tweaked comments in certain examples using curl_multi_fdset().

The -O option caused curl to crash on windows and DOS due to the
tool writing out of boundary memory.

The feature that uses the file name given in a
Content-disposition: header didn't properly skip trailing
carriage returns and linefeed characters from the end of the file
name when it was given without quotes.

Make the function call with (void) as we don't care about the
return code.