Make it possible to run a test only in the standard variant.

Use this for mjsunit/unicode-case-overoptimization, which is not
related to Crankshaft at all and takes ages.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/27704002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17255 ce2b1a6d-e550-0410-aec6-3dcde31c8c00