how to build 64bit xapian using MSVC2017?

[Olly Betts]

On Tue, Mar 20, 2018 at 08:28:24PM +0000, Olly Betts wrote:
> Related to this, the appveyor build is currently failing on git master.
> Unfortunately the change at which is started to fail was the addition
> of the new "honey" backend, which doesn't narrow things down to a
> useful degree.

I've disabled honey in these builds for now.  This really needs to be
addressed, but having the build green so we can spot quickly if other
issues are introduced seems more productive than leaving it red for a
long time.

I've also added 64-bit CI builds for mingw64 and MSVS 2017.  The former
works with the remote backend enabled (the 64-bit SOCKET issue is
actually not a problem in practice it seems) but the latter fails with
what looks like a NULL pointer access in replication tests (the remote
backend and replication use the same network code).

I tried a MSVS 2015 64-bit build but that seemed to result in programs
linked to libxapian failing on start-up with no error message.  32-bit
builds with MSVS 2015 and 2017 work fine with the remote backend and
replication.

This is all backported to the RELEASE/1.4 branch and the CI builds are
green there too:

https://ci.appveyor.com/project/ojwb/xapian/build/44

These changes will be in 1.4.6 once released.  Meanwhile snapshots from
here should work (you'll want 1.4.5_git268 or later which is currently
being generated as I write so should be there shortly):

https://oligarchy.co.uk/xapian/RELEASE/1.4/

I've also added some notes on building with autotools and MSVC to
xapian-core's INSTALL file.

I'd love it if we could eliminate the various remaining problems -
patches would be great, but at least working out what's going wrong
would be useful.

Cheers,
    Olly