JMAP support will be optional for 3.0

[Robert Stepanek]

Hi,

I just pushed a patch in master to make JMAP support optional and
disabled by default for Cyrus 3.0. [1]

We decided to do this, because the JMAP http module depends on Xapian
search and we don't want to force all installations to use the custom
Xapian fork from cyruslibs [2], wether they use JMAP or not. If you want
to use JMAP, please make sure to run ./configure with the
--enable-xapian and --enable-jmap options and to use the cyruslibs
submodules.

We are in active discussion with the Xapian team to merge our custom
fork into upstream. In fact, we already did so for some features. Making
JMAP optional is purely a temporary, technical decision. We keep working
on it daily and it's already rocking.

Cheers,
Robert

[1]
https://github.com/cyrusimap/cyrus-imapd/commit/892c3bdeaebbf1196000ad954468783a2e112ecb
[2] https://github.com/cyrusimap/cyruslibs