util: determine object types in C++

Determine object types of regular expressions, Dates, Maps, and
Sets in the C++ layer instead of depending on toString()
behavior in JavaScript.

PR-URL: https://github.com/nodejs/node/pull/4100


Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>