Panic on ENOMEMs

Panic on ENOMEMs

Trying to recover is incorrect because we don't want to advertise an
incomplete or outdated VRP table to the routers. We don't want to rely
on the OOM-killer; we NEED to die on memory allocation failures ASAP.

Though this doesn't have much to do with the RRDP refactor, I'm doing it
early to get plenty of time for testing and review.

Partially F1xes #40. (Still need to update some dependency usages.)