Log Message:
Import verifast-17.06 as devel/verifast.

VeriFast is a research prototype of a tool for modular formal
verification of correctness properties of single-threaded and
multithreaded C and Java programs annotated with preconditions and
postconditions written in separation logic.

This is recommended by Kiwamu Okabe in Japan NetBSD Users' Group BOF 2017
at the University of Tokyo.