[DAGCombiner] (add X, (adde Y, 0, Carry)) -> (adde X, Y, Carry)

Summary: This is extracted from D29443 .

Reviewers: mkuper, spatel, RKSimon, zvi, bkramer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29564

llvm-svn: 294186