[turbofan] Fix lowering of typed loads/stores.

[turbofan] Fix lowering of typed loads/stores.

We can only access to external typed arrays; lowering of internal
typed arrays would require a map check plus eager deoptimization.
Also embed the array buffer reference directly instead of embedding
the typed array.

TEST=cctest,mjsunit,unittests
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/621863002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24386 ce2b1a6d-e550-0410-aec6-3dcde31c8c00