Allow both "--no<flag>" and "--no-<flag>" to disable <flag>.

We shouldn't need to know whether to use --no or --no- as prefix.
The latter is more intuitive and also what chromium uses.

R=machenbach@chromium.org
BUG=

Review URL: https://codereview.chromium.org/22851009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16261 ce2b1a6d-e550-0410-aec6-3dcde31c8c00