Closes #733

This is a follow up to the previous commit.

Closes #492

Skipping the scripts dir is primarily done for 'make install' so that it
does not attempt to install the zsh completion script as we've not yet
found a proper way to do/run that at install time.

By leaving the script dir's Makefile in place, a user can still opt to
run make install manually in there.

Closes #620

... to make them appear as links on the html version.

Renamed the header and source files for this module as they are HTTP
specific and as such, they should use the naming convention as other
HTTP authentication source files do - this revert commit 260ee6b7.

Note: We could also rename curl_ntlm_wb.[c|h], however, the Winbind
code needs separating from the HTTP protocol and migrating into the
vauth directory, thus adding support for Winbind to the SASL based
protocols such as IMAP, POP3 and SMTP.

Closes #677

usage: "statvfs path"
returns remote file system statistics

Fixed failed redirection of stderr with some options. At least on Msys2,
perl fails to redirect stderr if $value contains newline or other weird
characters.

libidn's tld_check_lz returns an error offset of the first character
that it failed to process, however that offset is not a byte offset and
may not even be in the locale encoding therefore we can't use it to show
the user the character that failed to process.

Bug: https://github.com/curl/curl/issues/731
Reported-by: Karlson2k

As the GSS-API and SSPI based source files are no longer library/API
specific, following the extraction of that authentication code to the
vauth directory, combine these files rather than maintain two separate
versions.

Part 2 of 2 - Moved the GSS-API based Negotiate authentication code.

Part 1 of 2 - Moved the SSPI based Negotiate authentication code.

Not picked up by checksrc or Visual Studio but my own code review, this
would haven broken Intel based Unix builds - Perhaps I should learn to
type on my laptop's keyboard before committing!

warning C4244: '=': conversion from 'int' to 'unsigned short', possible
                    loss of data

Closes #729
Closes #728

Renamed all the SASL functions that moved to the new vauth directory to
include the correct module name.

As most of this work was performed in 2015 but not pushed until 2016
updated the copyright year to reflect the public facing changes.

Updated the makefiles and Visual Studio project files to support moving
the authentication code to the new lib/vauth directory that was started
in commit 0d04e859.

Add ALPN support for schannel. This allows cURL to negotiate
HTTP/2.0 connections when built with schannel.

Closes #724