[MemDep] DBG intrinsics don't impact abort limit for call site dependence analysis

Summary:
Memory dependence analysis no longer counts DbgInfoIntrinsics towards the
limit where to abort the analysis. Before, a bunch of calls to dbg.value
could affect the generated code, meaning that with -g we could generate
different code than without.

Reviewers: chandlerc, Prazek, davide, efriedma

Reviewed By: efriedma

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39181

llvm-svn: 316551