Drop support for pre-1.4 Xapian, prepare for 1.5.x

[David Bremner]

David Bremner <david at tethera.net> writes:

> The current development release of Xapian drops several deprecated
> APIs. This hampers testing of notmuch against Xapian master (i.e. to
> see if a problem has been fixed). This series fixes most of the
> incompatibilities.
>
> The one thing this series doesn't handle is test/T530-upgrade.sh,
> which mostly fails because Xapian 1.5 / master drops support for
> Chert. I think that we should probably deprecate support for notmuch
> v1 databases. These were replaced by version 2 in 2010. I think more
> thought is probably needed for this migration so I left those failing
> tests for now.  This isn't quite as scary as it sounds, because we
> really only support stable releases of Xapian, so the chert removal
> effectively won't happen until 1.6.
>

I forgot, there's one other failing test with xapian 1.5

T650-regexp-query: Testing regular expression searches
 FAIL   null from: search
	--- T650-regexp-query.7.EXPECTED	2019-04-15 11:03:10.128070898 +0000
	+++ T650-regexp-query.7.OUTPUT	2019-04-15 11:03:10.128070898 +0000
	@@ -1 +0,0 @@
	-thread:XXX   2001-01-05 [1/1] -; empty from (inbox unread)