Update v8heapconst.py

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/170263002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19424 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Also compile A64 for quickcheck target

We don't run tests yet because even in release mode, this will take a
considerable amount of time.

BUG=none
R=ulan@chromium.org, machenbach@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/169303006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19425 ce2b1a6d-e550-0410-aec6-3dcde31c8c00