Migration to rust-lightning 0.0.112

[tnull]

We should do the following things after the upcoming release of rust-lightning 0.0.112:

• Migrate to upstream logging macros (see Export and document all log macros. rust-lightning#1682)
• Remove return value from register_output (see Drop return value from Filter::register_output rust-lightning#1663)
• Consider using an async background processor (see Add a background processor which is async rust-lightning#1657)

[tnull]

Closing, last point is covered by #37.