ARM64: unit tests for instruction selection.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/464773004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23099 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Add FOR_INT32_SHIFTS to value-helper.h

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/470533002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23100 ce2b1a6d-e550-0410-aec6-3dcde31c8c00