Various cleanups in check elimination.

Various cleanups in check elimination.

- Move IsMapAccess() to HObjectAccess.
- Collect the actual objects instead of HStoreNamedFields in
  effects, and also consider HTransitionElementsKind.
- Fix ownership of HCheckMaps::maps() and HLoadNamedField::maps().
- Avoid heavy copying of the same map sets all the time during
  check elimination, and do something useful with the memory
  instead by slightly bumping the maximum number of tracked
  objects.
- Slightly optimize UniqueSet::Contains().

R=svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21133

[Benedikt Meurer, 2014-05-05 06:47:33]

Hey Sven,
Next step towards using map stability during check elimination.
PTAL
-- Benedikt

[Sven Panne, 2014-05-05 06:52:37]

lgtm

[Benedikt Meurer, 2014-05-05 06:53:34]

Committed patchset #1 manually as r21133 (presubmit successful).