Previously, we just ignored error code passed to
on_stream_close_callback and just return 0 (success) after stream
closure even if stream was reset with error.  This patch records error
code in on_stream_close_callback, and return -1 and use CURLE_HTTP2
error code on abnormal stream closure.

Pointed-out-by: Tatsuhiro Tsujikawa
Bug: http://curl.haxx.se/bug/view.cgi?id=1487

In that case, we only skip writing the error message for failed NSS
initialization (while still returning the correct error code).

The vtls layer now checks the return value, so it is no longer necessary
to abort if a random number cannot be provided by NSS.  This also fixes
the following Coverity report:

Error: FORWARD_NULL (CWE-476):
lib/vtls/nss.c:1918: var_compare_op: Comparing "data" to null implies that "data" might be null.
lib/vtls/nss.c:1923: var_deref_model: Passing null pointer "data" to "Curl_failf", which dereferences it.
lib/sendf.c:154:3: deref_parm: Directly dereferencing parameter "data".

This reverts commit 03fa5768.

obj_count can be 1 if the custom read function is set or the stdin
handle is a reference to a pipe. Since the pipe should be handled
using the PeekNamedPipe-check below, the custom read function should
only be used if it is actually enabled.

According to [1]: "Returning 0 will signal end-of-file to the library
and cause it to stop the current transfer."
This change makes the Windows telnet code handle this case accordingly.

 [1] http://curl.haxx.se/libcurl/c/CURLOPT_READFUNCTION.html

... even if the last IPv6 connection attempt has failed.

Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1187531#c4

... in case the protocol versions are mixed in a DNS response
(IPv6 -> IPv4 -> IPv6).

Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1187531#c3

SSL_CTX_load_verify_locations by default (and if given non-Null
parameters) searches the CAfile first and falls back to CApath.  This
allows for CAfile to be a basis (e.g. installed by the package manager)
and CApath to be a user configured directory.

This wasn't reflected by the previous configure constraint which this
patch fixes.

Bug: https://github.com/bagder/curl/pull/139

Correctly check for memcmp() return value (it returns 0 if the strings match).

This is not really important, since curl is going to use http/1.1 anyway, but
it's still a bug I guess.

Correctly check for strncmp() return value (it returns 0 if the strings
match).

lib/vtls/openssl.c:1450:7: warning: extra tokens at end of #endif directive

For consistency with other conditionally compiled code in openssl.c,
use OPENSSL_IS_BORINGSSL rather than HAVE_BORINGSSL and try to use
HAVE_BORINGSSL outside of openssl.c when the OpenSSL header files are
not included.

Versions of OpenSSL prior to v0.9.8h do not support the necessary
functions for OCSP stapling.

Previously we don't ignore PUSH_PROMISE header fields in on_header
callback.  It makes header values mixed with following HEADERS,
resulting protocol error.

Prior to this change the options for exclusive SSL protocol versions did
not actually set the protocol exclusive.

http://curl.haxx.se/mail/lib-2015-01/0002.html
Reported-by: Dan Fandrich

Removed the curl_ prefix from the schannel source files as discussed
with Marc and Daniel at FOSDEM.

The struct went private in 1.0.2 so we cannot read the version number
from there anymore. Use SSL_version() instead!

Reported-by: Gisle Vanem
Bug: http://curl.haxx.se/mail/lib-2015-02/0034.html

The previous one was "encumbered" by RSA Inc - to avoid the licensing
restrictions it has being replaced. This is the initial import,
inserting the md5.c and md5.h files from
http://openwall.info/wiki/people/solar/software/public-domain-source-code/md5

Code-by: Alexander Peslyak

The previous one was "encumbered" by RSA Inc - to avoid the licensing
restrictions it has being replaced. This is the initial import,
inserting the md4.c and md4.h files from
http://openwall.info/wiki/people/solar/software/public-domain-source-code/md4

Code-by: Alexander Peslyak

Better use of 80 character line limit, comment corrections and line
spacing preferences.