Better typing and type verification

Better typing and type verification

- Extend verifier to check types of JS and Simplified nodes.
- Untyped nodes now contain NULL as types, enforcing hard failure.
- Typer immediately installs itself as a decorator; remove explicit decorator installation.
- Decorator eagerly types all nodes that have typed inputs
  (subsumes typing of constant cache, removing its typing
  side-channel and various spurious dependencies on the typer).
- Cut down typer interface to prevent inconsistently typed graphs.
- Remove verification from start, since it caused too much trouble
  with semi-wellformed nodes.
- Fix a couple of bugs on the way that got uncovered.

To do: verifying machine operators. Also, various conditions in the
verifier are currently commented out, because they don't yet hold.

BUG=
R=jarin@chromium.org,titzer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=24626

[rossberg, 2014-10-14 14:49:36]

rossberg@chromium.org changed reviewers:
+ jarin@chromium.org, titzer@chromium.org

[rossberg, 2014-10-15 11:38:33]

Committed patchset #2 manually as 24626.