...due to the newly added CURL_SSLVERSION_MAX_* functionality

Verified with OpenSSL 1.1.0e and OpenSSL master (1.1.1)

This commit introduces the CURL_SSLVERSION_MAX_* constants as well as
the --tls-max option of the curl tool.

Closes https://github.com/curl/curl/pull/1166

Assisted-by: Ray Satiro
Bug: https://curl.haxx.se/mail/lib-2017-03/0002.html

maketgz now runs scripts/updatemanpages.pl to update the man pages .TH
section to use the current date and curl/libcurl version.

(TODO Section 3.1)

Closes #1058

Ignore man page dist files generated by scripts/updatemanpages.pl

Added script to update man pages to use the current date and
curl/libcurl versions.

updatemanpages.pl has three arrays: list of directories to look in,
list of extensions to process, list of files to exclude from
processing.

Check man page in git repoistory using the date from the existing man
page before updating to avoid updating the man page if no change is
made.

If data is received from the git command then update the man page with
the current date and version otherwise leave alone.

Applied patch from badger to make the date argument optional, change the
git command used, added date argument to processfile subroutine and
print to STDERR if no date is found in a man page.

Added code to process the changed man page into a new man page with
.dist added to the filename to keep the original source files unchanged.
Updated POD documentation to reflect that the date argument optional.

Code style is in line with CODE_STYLE.md.

Directories: docs/ docs/libcurl/ docs/libcurl/opts/ tests/
Extensions: .1 .3
Excluded files: mk-ca-bundle.1 template.3

(TODO Section 3.1)

This fixes assertion error which occurs when redirect is done with 0
length body via HTTP/2, and the easy handle is reused, but new
connection is established due to hostname change:

    curl: http2.c:1572: ssize_t http2_recv(struct connectdata *,
      int, char *, size_t, CURLcode *):
    Assertion `httpc->drain_total >= data->state.drain' failed.

To fix this bug, ensure that http2_handle_stream is called.

Fixes #1286
Closes #1302

Assisted-by: Ray Satiro

Bug: https://curl.haxx.se/mail/lib-2017-03/0009.html

Bug: https://github.com/curl/curl/issues/1308
Reported-by: Justin Clift

... because it causes confusion with users. Example URLs:

"http://[127.0.0.1]:11211:80" which a lot of languages' URL parsers will
parse and claim uses port number 80, while libcurl would use port number
11211.

"http://user@example.com:80@localhost" which by the WHATWG URL spec will
be treated to contain user name 'user@example.com' but according to
RFC3986 is user name 'user' for the host 'example.com' and then port 80
is followed by "@localhost"

Both these formats are now rejected, and verified so in test 1260.

Reported-by: Orange Tsai

Closes #1312

Reported-by: Peter Pentchev

Reported-by: Giuseppe Persico

Pointed-out-by: Ray Satiro
Bug: https://curl.haxx.se/mail/lib-2017-03/0004.html

Ref: https://github.com/curl/curl/pull/1228

Ref: https://github.com/curl/curl/pull/1228

Assisted-by: Simon Warta <simon@kullo.net>
Ref: https://github.com/curl/curl/pull/1228

This is closer to how configure.ac does it

Ref: https://github.com/curl/curl/pull/1228

.. also document that CURLE_NOT_BUILT_IN is a RETURN VALUE.

Ref: https://github.com/curl/curl/pull/1290

MSVC with LTCG detects this at warning level 4.

Closes #1304

Move the proxy parse/init into helper create_conn_helper_init_proxy to
mitigate the chances some non-proxy code will be mistakenly added to it.

Ref: https://github.com/curl/curl/issues/1274#issuecomment-281556510
Ref: https://github.com/curl/curl/pull/1293

Closes https://github.com/curl/curl/pull/1298

Mark intended fallthroughs with /* FALLTHROUGH */ so that gcc will know
it's expected and won't warn on [-Wimplicit-fallthrough=].

Closes https://github.com/curl/curl/pull/1297

Prior to this change if you attempted to configure curl using
--wtih-zlib and specified a path the path would be ignored if you also
had pkg-config installed on your system.  This situation can easily
arise when you are cross compiling.  This change moves the test for
detecting zlib settings via pkg-config only if OPT_ZLIB is not set.

Closes https://github.com/curl/curl/pull/1292

Closes https://github.com/curl/curl/pull/1301

Better handle options conflicts that can occur if --enable-pthreads.

Bug: https://github.com/curl/curl/pull/1295
Reported-by: Marc-Antoine Perennou

In DarwinSSL the SSLSetPeerDomainName function is used to enable both
sending SNI and verifying the host. When host verification is disabled
the function cannot be called, therefore SNI is disabled as well.

Closes https://github.com/curl/curl/pull/1240

If size_t is 32 bits, MSVC warns:
warning C4310: cast truncates constant value
The warning is harmless as CURL_MASK_SCOFFT gets
truncated to the maximum value of size_t.