Increase external allocation limit.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/291653005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21425 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Allow specifying base offset when constructing Keyed hydrogen instructions

This is preparation for pending hydrogen stub work that needs to access memory using KeyedLoad/KeyedStore operations where the base offset used for the accesses are is the the default (e.g. the size of an FixedArray header for FixedArrays or zero for external arrays).

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/295913009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21426 ce2b1a6d-e550-0410-aec6-3dcde31c8c00