Periodic cluster synchronisation calls isMaster() which currently resends the
"client" metadata every call - the spec specifies:

	isMaster commands issued after the initial connection handshake MUST NOT
	contain handshake arguments

	https://github.com/mongodb/specifications/blob/master/source/mongodb-handshake/handshake.rst#connection-handshake

This hotfix prevents subsequent isMaster calls from sending the client metadata
again - fixes globalsign#101 and fixes globalsign#103.

Thanks to @changwoo-nam @qhenkart @canthefason @jyoon17 for spotting the initial
issue, opening tickets, and having the problem debugged with a PoC fix before I
even woke up.

* Brings in a patch on having flusher not suppress errors. (globalsign#81)

go-mgo#360

* Fallback to JSON tags when BSON tag isn't present (globalsign#91)

* Fallback to JSON tags when BSON tag isn't present


Cleanup.

* Add test to demonstrate tagging fallback.

- Test coverage for tagging test.

* socket: only send client metadata once per socket

Periodic cluster synchronisation calls isMaster() which currently resends the
"client" metadata every call - the spec specifies:

	isMaster commands issued after the initial connection handshake MUST NOT
	contain handshake arguments

	https://github.com/mongodb/specifications/blob/master/source/mongodb-handshake/handshake.rst#connection-handshake

This hotfix prevents subsequent isMaster calls from sending the client metadata
again - fixes globalsign#101 and fixes globalsign#103.

Thanks to @changwoo-nam @qhenkart @canthefason @jyoon17 for spotting the initial
issue, opening tickets, and having the problem debugged with a PoC fix before I
even woke up.

* Cluster abended test 254 (globalsign#100)

* Add a test that mongo Server gets their abended reset as necessary.

See https://github.com/go-mgo/mgo/issues/254 and
https://github.com/go-mgo/mgo/pull/255/files

* Include the patch from Issue 255.

This brings in a test which fails without the patch, and passes with the
patch. Still to be tested, manual tcpkill of a socket.

* changeStream support (globalsign#97)

Add $changeStream support

* readme: credit @peterdeka and @steve-gray (globalsign#110)

* cluster: fix deadlock in cluster synchronisation (globalsign#120)

For a impressively thorough breakdown of the problem, see:
	globalsign#120 (comment)

Huge thanks to @dvic and @KJTsanaktsidis for the report and fix.

* readme: credit @dvic and @KJTsanaktsidis

Release/r2018.04.23