Pull in commit

https://github.com/ethomson/ntlmclient/commit/e7b2583e1bc28c33c43854e7c318e859b4e83bef

to fix #5353.

The ntlmclient dependency has quite a lot of places with implicit
fallthroughs. As at least modern GCC has enabled warnings on
implicit fallthroughs by default, the developer is greeted with a
wall of warnings when compiling that dependency.

Disable implicit fallthrough warnings for ntlmclient to fix this
issue.

When the end of the host is reached, and we're at the colon separating
the host with the port (ie, there is no numeric port) then do not error.
This is allowed by RFC 3986.

Include https://github.com/ethomson/ntlmclient as a dependency.

Our PCRE dependency has uncommented fallthroughs in switch statements.
Turn off warnings for those in the PCRE code.

PCRE includes compatibility functions that may go unused.  Don't warn.

Use PCRE 8.42 as the builtin regex implementation, using its POSIX
compatibility layer.  PCRE uses ASCII by default and the users locale
will not influence its behavior, so its `regcomp` implementation is
similar to `regcomp_l` with a C locale.