src: remove VS 2013 compatibility hacks

We can remove some Visual Studio 2013-specific workarounds now that
support for that compiler has officially been dropped.

PR-URL: https://github.com/nodejs/node/pull/8067
Refs: https://github.com/nodejs/node/issues/7484
Refs: https://github.com/nodejs/node/pull/8049


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joao Reis <reis@janeasystems.com>