Made the v8_utils target compile under a modern version of v8.
v8 API updates for run_tests.cc.
Applied a nasy hack to enable v8's native support for typed arrays.

On my OS X system with v8 version 3.19.18.4, this appears to work for
all but the DataView class. As far as I can tell the modern version of
v8 supports this class too.
Slightly cleaned up the hack from 195b4eb6490ac3ae84a685e96b2bb3034790e308.