Flush the header stream when -D is used so that they are sent off
earlier.

Bug: https://github.com/bagder/curl/issues/324
Reported-by: Cédric Connes

Reported-by: bemoody
Bug: https://github.com/bagder/curl/issues/325

Since we do prefix match using given header by application code
against header name pair in format "NAME:VALUE", and VALUE part can
contain ":", we have to careful about existence of ":" in header
parameter.  ":" should be allowed to match HTTP/2 pseudo-header field,
and other use of ":" in header must be treated as error, and
curl_pushheader_byname should return NULL.  This commit implements
this behaviour.

Following the fix made in 903b6e05.

... to properly support that options are set to the handle after it is
added to the multi handle.

Bug: http://curl.haxx.se/mail/lib-2015-06/0122.html
Reported-by: Stefan Bühler

Advise that WinSSL in versions <= XP will not be able to connect to
servers that no longer support the legacy handshakes and algorithms used
by those versions, and to use an alternate backend like OpenSSL instead.

Bug: https://github.com/bagder/curl/issues/253


Reported-by: zenden2k <zenden2k@gmail.com>

... in commit curl-7_43_0-18-g570076e

In 3013bb6b I had changed cookie export to ignore any-domain cookies,
however the logic I used to do so was incorrect, and would lead to a
busy loop in the case of exporting a cookie list that contained
any-domain cookies. The result of that is worse though, because in that
case the other cookies would not be written resulting in an empty file
once the application is terminated to stop the busy loop.

libcurl can still be built with it, even if the tool is not. Maintain
independence!

It is similar to existing CURL_CFLAG_EXTRAS, but for
extra linker option.

Coverity CID 1306668

Make sure that the error buffer is always initialized and simplify the
use of it to make the logic easier.

Bug: https://github.com/bagder/curl/issues/318
Reported-by: sneis

Using this fixed format for example descriptions, we can generate a
better list on the web site.

OPENSSL_load_builtin_modules does not exist in BoringSSL. Regression
from cae43a10

The symbol SSL3_MT_NEWSESSION_TICKET appears to have been introduced at
around openssl 0.9.8f, and the use of it in lib/vtls/openssl.c breaks
builds with older openssls (certainly with 0.9.8b, which is the latest
older version I have to try with).

** WORK-AROUND **

The introduced non-blocking general behaviour for Curl_proxyCONNECT()
didn't work for the data connection establishment unless it was very
fast. The newly introduced function argument makes it operate in a more
blocking manner, more like it used to work in the past. This blocking
approach is only used when the FTP data connecting through HTTP proxy.

Blocking like this is bad. A better fix would make it work more
asynchronously.

Bug: https://github.com/bagder/curl/issues/278