[c-lightning] c-lightning release v0.9.1: The Antiguan BTC Maximalist Society

[Rusty Russell]

We're pleased to announce the 0.9.1 release of c-lightning, named by Jon
Griffiths.

	https://github.com/ElementsProject/lightning/releases/tag/v0.9.1

This is a significant release with major bugfixes to multi-part payments
and various notable speedups and improvements across the board.

*Did you know*: c-lightning deprecates features with 6 months warning, and
you can set allow-deprecated-apis=false to test?

Highlights for Users

* The sending of multi-part payments has seen a lot of work, covering
  more corner cases and generally becoming much more robust.

* New official plugins create commands multiwithdraw and
  multifundchannel to easily produce a single transaction which does
  more than one thing; these use the PSBT plumbing created for v0.9.0.
  
* We produce far less log spam when log-level is set to debug, so if
  you've avoided setting that before, I recommend trying now.
   
* Startup checks that bitcoind is the correct version, and relays
  transactions

* Builtin plugins are now nominated as important, and you can nominate
  others as important too. The daemon will stop if these fail.

* You can now build a postgres-only installation, without sqlite3.

Highlights for the Network

* Our invoices now supply more than one routehint if we think you'll
  need to use multi-part-payments.

* We prune channels which are not updated in both directions every 2
  weeks.

* Our default CTLV expiry has increased to 34 blocks, or 18 if we're the
  final node, as per updated specification recommendations
  (https://github.com/lightningnetwork/lightning-rfc/pull/785)

Highlights for Developers

* PSBT APIs fleshed out with utxopsbt and locktime arguments.

* Plugins can easily mark commands and options deprecated.

* The new channel_state_changed notification lets plugins easily track
  channel behavior.

More details can be found at

        https://github.com/ElementsProject/lightning/blob/v0.9.1/CHANGELOG.md

Thanks to everyone for their contributions and bug reports; please keep
them coming.

Since 0.9.0, we've had 391 commits commits from 15 different authors.
A special thanks goes to the 3 first time contributors:

    Matt Whitlock @whitslack
    Sergi Delgado Segura @sr-gi
    Moller40 @Moller40

Cheers,
Christian, Rusty, ZmnSCPxj, and Lisa