NewGVN: Handle coercion of constant stores, loads, memory insts.

NewGVN: Handle coercion of constant stores, loads, memory insts.

Summary:
Depends on D30928.

This adds support for coercion of stores and memory instructions that do not require insertion to process.
Another few tests down.
I added the relevant tests from rle.ll

Reviewers: davide

Subscribers: llvm-commits, Prazek

Differential Revision: https://reviews.llvm.org/D30929

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299330 91177308-0d34-0410-b5e6-96231b3b80d8