Merge pull request #2800 from optout21/channel-close-add-funding

Add channel funding txo to Channel Event::ChannelClosed

diff --cc lightning/src/events/mod.rs
Simple merge

diff --cc lightning/src/ln/channel.rs
Simple merge

diff --cc lightning/src/ln/channelmanager.rs
Simple merge

diff --cc lightning/src/ln/functional_tests.rs
Simple merge