MIPS: CheckPrototypes uses weak cells to embed maps.

Port 062a032f50291ce181462226ff41b4ef9b11deba

BUG=v8:3629
LOG=N

Review URL: https://codereview.chromium.org/777673002

Cr-Commit-Position: refs/heads/master@{#25645}
Reland "[turbofan] Reuse forward fixpoint algorithm in Typer by making it a Reducer."

This reverts commit 918ef9d712ab77bc33ffb8eb985a6fd5672602f6.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/780623002

Cr-Commit-Position: refs/heads/master@{#25646}
MIPS: Use weak cells to embed maps in store handler.

Port 3fc9c9b665baaa434c672efcbff632a2eae86f56

BUG=v8:3629
LOG=N

Review URL: https://codereview.chromium.org/762483004

Cr-Commit-Position: refs/heads/master@{#25647}