MSVC 12 complains:

lib\vtls\openssl.c(1554): warning C4701: potentially uninitialized local
variable 'verstr' used It's a false positive, but as it's normally not,
I have enabled warning-as-error for that warning.

Currently, libcurl rejects responses with "Content-Encoding: compress"
when CURLOPT_ACCEPT_ENCODING is set to "". I think that libcurl should
treat the Content-Encoding "compress" the same as other
Content-Encodings that it does not support, e.g. "bzip2". That means
just ignoring it.

To make it easier to link with static versions of OpenSSL, the configure
script now checks if -ldl is needed for linking.

Help-by: TJ Saunders

- Set CURLOPT_SSL_OPTIONS only if the tool enabled an SSL option.

Broken by me several days ago in 172b2be.
curl@172b2be#diff-70b44ee478e58d4e1ddcf9c9a73d257b

Bug: http://curl.haxx.se/mail/lib-2015-07/0119.html
Reported-by: Dan Fandrich

Closes curl#349 for now

Closes curl#322 for now

Closes curl#355

...as well as some wording.

This is a new document to consolidate our thread safety information from
several documents (curl-www:features, libcurl.3, libcurl-tutorial.3).
Each document's section on multi-threading will now point to this one.

.. also update formatting and add WinSSL and wolfSSL to the SSL/TLS
handlers list.

Following commit 957fcd9 and in preparation for adding the VC14
project files renamed the curl source project files.

This wasn't possible with the old curlsrc project filenames, but like
commit 2a615a2 and 11397eb for libcurl use the built in Visual
Studio macros for the output filenames.

Visual Studio project files and updates to makefile.am to follow.

Whilst there are no coding standards for the batch files used in curl,
most tend to use lower-case for keywords and upper-case for variables.

Updates to Makefile.am for the generation of the project files in
the tarball to follow.

Because the 'not' operator has a very low precedence and as a result the
entire statement was erroneously negated and could never be true.

Closes curl#466

Closes curl#469

Closes curl#471

- If a CURLINFO option is unknown return CURLE_UNKNOWN_OPTION.

Prior to this change CURLE_BAD_FUNCTION_ARGUMENT was returned on
unknown. That return value is contradicted by the CURLINFO option
documentation which specifies a return of CURLE_UNKNOWN_OPTION on
unknown.

'make V=1' will make the build verbose like before

Follow up to 613e502.

... since some compilers don't have it and instead use other types, such
as __int64.

Reported by: gkinseyhpw
Closes curl#478

Closes curl#479

If the underlying recv called by http2_recv returns -1 then that is the
value http2_recv returns to the caller.

... as in the polarssl TLS backend for example it uses memory functions.

follow-up from 6f8ecea

It makes it a clearer message for developers reaching that point without
the necessary support.

Thanks-by: Jay Satiro

Closes curl#78

sk_X509_pop will decrease the size of the stack which means that the loop would
end after having added only half of the certificates.

Also make sure that the X509 certificate is freed in case
SSL_CTX_add_extra_chain_cert fails.

... and allow it to get set by a caller easier.

Reported-by: Rainer Jung
Bug: http://curl.haxx.se/mail/lib-2015-10/0035.html