When the host name in a URL is given as an IPv4 numerical address, the
address can be specified with dotted numericals in four different ways:
a32, a.b24, a.b.c16 or a.b.c.d and each part can be specified in
decimal, octal (0-prefixed) or hexadecimal (0x-prefixed).

Instead of passing on the name as-is and leaving the handling to the
underlying name functions, which made them not work with c-ares but work
with getaddrinfo, this change now makes the curl URL API itself detect
and "normalize" host names specified as IPv4 numericals.

The WHATWG URL Spec says this is an okay way to specify a host name in a
URL. RFC 3896 does not allow them, but curl didn't prevent them before
and it seems other RFC 3896-using tools have not either. Host names used
like this are widely supported by other tools as well due to the
handling being done by getaddrinfo and friends.

I decided to add the functionality into the URL API itself so that all
users of these functions get the benefits, when for example wanting to
compare two URLs. Also, it makes curl built to use c-ares now support
them as well and make curl builds more consistent.

The normalization makes HTTPS and virtual hosted HTTP work fine even
when curl gets the address specified using one of the "obscure" formats.

Test 1560 is extended to verify.

Fixes #6863
Closes #6871

No longer considered experimental.

Closes #6700

Make sure one of the azure jobs has jsonlint installed so that the test
runs there.

Ref: #6905

Update test 970 accordingly.

Reported-by: Michal Rus
Fixes #6905
Closes #6906

Signed-off-by: Victor Vieux <victorvieux@gmail.com>

Closes #6895

Makes the option more explicit.

Closes #6887

Add test 676 to verify that setting CURLOPT_COOKIEFILE to NULL again clears
the cookiejar from memory.

Reported-by: Stefan Karpinski
Fixes #6889
Closes #6891

According to Microsoft document MS-NLMP, current flags usage is not
accurate: flag NTLMFLAG_NEGOTIATE_NTLM2_KEY controls the use of
extended security in an NTLM authentication message and NTLM version 2
cannot be negotiated within the protocol.

The solution implemented here is: if the extended security flag is set,
prefer using NTLM version 2 (as a server featuring extended security
should also support version 2). If version 2 has been disabled at
compile time, use extended security.

Tests involving NTLM are adjusted to this new behavior.

Fixes #6813
Closes #6849

This was previously defined by the obsolete AC_TYPE_SIGNAL macro,
which was removed in 2682e5f5. The deprecation text says

> Your code may safely assume C89 semantics that RETSIGTYPE is void.

So, remove it and just use void instead.

Closes #6861