Had a bug in my aoc lib, that lost me an hour for pt 1:
The ADJ dict has SW twice, and lacks NE.
The bug is at least 2 years old. It was introduced in 661f18dca4
and apparently has never worked. I guess it has not been used
up until now.
That being said, it was straight-forward. A new helper for
grid was used the first time, as well as an improved vdbg()
function.
