Closes #1557

Closes https://github.com/curl/curl/pull/1539

... and update the certinfo.c example accordingly.

Fixes https://github.com/curl/curl/issues/846

Fixes #1524

... since closesocket is a function in WinSock.

Reported-by: Marcel Raad
Bug: https://github.com/curl/curl/commit/55fcb8485914700132fd1854c9509b66c955efbe#co
mmitcomment-22347818

Reported-by: Gisle Vanem

Fixes #1208

Closes #1509

This is contained in -Wextra with GCC 7.

Test 1261 added to verify.

Reported-by: Lloyd Fournier

Fixes #1489
Closes #1497

It takes someone to read up on the APIs of these libraries to figure out
how to do this correctly.

Reported-by: Michael Kaufmann

Closes #1253

That means delete the timer.

Reported-by: Michael Kaufmann
Ref: #1253

Since the man page generator wants the long option name version to
generate the proper output.

Closes #1400

follow-up to 5ddad099

Some code (e.g. Curl_fillreadbuffer) assumes that this buffer is not
exceedingly tiny and will break if it is. This same check is already
done at run time in the CURLOPT_BUFFERSIZE option.

... I found them in the commit logs from the early years

... and delete trailing whitespace

Fixes #1484

clang 5.0 complains:
possible misuse of comma operator here [-Wcomma]

... using the docs/cmdline-opts/gen.pl script, so that we get all the
command line option documentation from the same source.

The generation of the list has to be done manually and pasted into the
source code.

Closes #1465

... to also make it update when we remove files, like we did for
--environment in commit a8e388dd.