Improve detection of C++11 features.

Also improve detection of V8_INFINITY while we're at it.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/23323003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16254 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Adding missing operator!= for Handle and Persistent.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/22932004

Patch from Marja Hölttä <marja@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16255 ce2b1a6d-e550-0410-aec6-3dcde31c8c00