src: enable vector ics on arm again

The flag is no longer supported by V8 4.5, and the original issue [1] on ARMv6
no longer manifests with (at least) 4.5.103.20.

[1] See https://code.google.com/p/v8/issues/detail?id=4338

PR-URL: https://github.com/nodejs/node/pull/2509


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>