This is the first CL in a series that add support for the harmony scoping
features to crankshaft. This CL specifically adds support for stack
allocated 'let' and 'const' declared variables in function scopes.

TEST=mjsunit/harmony/block-let-crankshaft.js

Review URL: http://codereview.chromium.org/8806012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10171 ce2b1a6d-e550-0410-aec6-3dcde31c8c00