[Attributor][Fix] Deal with "growing" dereferenceability

Summary:
If we have a negative inbounds offset dereferenceabily "grows". However,
until we do not handle the overflow that can occur in the
dereferenceable bytes and the problem with loops, we simply do not grow
the state.

Reviewers: sstefan1, uenoku

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66557

llvm-svn: 369771