Nuke CompareToNull AST node.

Nuke CompareToNull AST node.

The Great Master Plan is to move the recognition of special cases for
comparisons further down the compilation pipeline where more information is
available. This is a first step into this direction: The special handling of
equality comparisons involving null is pushed from the parser to the code
generators, removing the need for a special AST node. (There are rumors from
usually well-informed sources that this node type is actually a relic of ancient
crankshaft days...)

The next steps will be the unification of null/undefined handling and pushing
the special case handling in crankshaft even further down the pipeline, enabling
the recognition of cases like "var foo=null; if (foo === bar) ...", but these
will be in separate CLs.
Committed: http://code.google.com/p/v8/source/detail?r=9293

[fschneider, 2011-09-15 08:56:01]

LGTM.

I also like the new approach much better.