The `chainlag` is defined as the positive difference between the
height of the last block processed by the node and the best height
known by the bitcoin backend. The chainlag is positive when we are
still catching up with the blockchain, and `0` otherwise.
The `chainlag` is used as an additional offset to the CLTV values when
sending payments, allowing payments to be sent even before the chain
sync completes.
Any file in this directory which is executable and whose name only
consists of alphanumeric characters, space, '.', '-' or '_' will be
automatically loaded when lightningd starts (unless suppressed with
commandline options).
4d27efc039