After a few wasted hours hunting down the reason for slowness during a
TLS handshake that turned out to be because of TCP_NODELAY not being
set, I think we have enough motivation to toggle the default for this
option. We now enable TCP_NODELAY by default and allow applications to
switch it off.

This also makes --tcp-nodelay unnecessary, but --no-tcp-nodelay can be
used to disable it.

Thanks-to: Tim Rühsen
Bug: https://curl.haxx.se/mail/lib-2016-06/0143.html

Closes #835

Closes #768

Closes #662

Closes #885

merged #931

... and make the distros link a proper link

Closes https://github.com/curl/curl/pull/914

Explain how some FTP servers support the machine readable listing
format MLSD from RFC 3659 and compare it to LIST.

Ref: https://github.com/curl/curl/issues/906

Closes #896

Reported-by: Richard Gray
Bug: https://curl.haxx.se/mail/lib-2016-06/0136.html

... as previously the README.cmake would be picked and put at the bottom
of the docs page there and it wasn't very representative!

Closes #740

Closes #883

When CURLOPT_POSTFIELDS is set to an empty string libcurl will send a
zero-byte POST. Prior to this change it was documented as sending data
from the read callback.

This also changes the wording of what happens when empty or NULL so that
it's hopefully easier to understand for people whose primary language
isn't English.

Bug: https://github.com/curl/curl/issues/862
Reported-by: Askar Safin

- Remove some erroneous text.

Closes https://github.com/curl/curl/pull/865