Split class and smi check from array operations.

Split class and smi check from array operations.

Array loads and stores have explicit receiver class
check and index smi check instead of emitting the checks
as part of the original instruction.

This allows redundant checks before array operations
to be eliminated.
Committed: https://code.google.com/p/dart/source/detail?r=11385

[Vyacheslav Egorov (Google), 2012-08-27 13:59:52]

lgtm