Merge pull request #454 from TheBlueMatt/2020-01-fuzz-mega-value

Panic on txn with value > 21mill in ChannelMonitor::block_connected, Clean up fuzz targets a bit

diff --cc fuzz/src/chanmon_consistency.rs
Simple merge

diff --cc fuzz/src/chanmon_deser.rs
Simple merge

diff --cc fuzz/src/full_stack.rs
Simple merge

diff --cc fuzz/src/router.rs
Simple merge

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