Upgrade Number constructor to ES6.

Add missing constants, predicates and functions to the Number
constructor to have it offer what ES6 now specifies.

That is, extend it with:

 * isInteger(), isSafeInteger()
 * parseInt(), parseFloat()
 * EPSILON, MIN_SAFE_INTEGER, MAX_SAFE_INTEGER

LOG=N
R=mstarzinger@chromium.org
BUG=v8:3082

Review URL: https://codereview.chromium.org/124573002

Patch from Sigbjorn Finne <sigbjornf@opera.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18480 ce2b1a6d-e550-0410-aec6-3dcde31c8c00