util: adhere to `noDeprecation` set at runtime

Until now, the docs stated that `process.noDeprecation` could be set
at runtime, but before any modules were loaded. That was not true,
because `lib/internal/util.js` was loaded during the process startup
process, so setting the flag at runtime was pointless.

Minimal test case:

    process.noDeprecation = true;
    process.EventEmitter;

This patch moves checking `process.noDeprecation` to the place where
it was actually used.

PR-URL: https://github.com/nodejs/node/pull/6683


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>