Handle built-in function identical correctly

Handle built-in function identical correctly

The parser, rather than the backend, recognizes the built-in function identical
and replaces is with the old token for the === operator. This fixes compile
time constant handling of calls to identical.

Committed: https://code.google.com/p/dart/source/detail?r=21753

[srdjan, 2013-04-18 23:32:10]

lgtm

[hausner, 2013-04-19 16:26:14]

Committed patchset #1 manually as r21753 (presubmit successful).