Summary:
- move a few files from checkers/ so that nullsafe can depend on them
- nullsafe depends on a few files in biabduction/ via Errdesc (not the
biabduction analysis itself but some datatypes and functionality):
- when possible, I've moved the individual functions elsewhere, in absint/Decompile.ml
- nullsafe still depends on a function in Errdesc that unfortunately
depends on a bunch of biabduction datatypes like Prop(!) and some
other functionality that for now is embedded in biabduction
(substitution in SIL instructions).
Reviewed By: mityal
Differential Revision: D21351906
fbshipit-source-id: 757528120