repl: fix require('3rdparty') regression

Fix module loading of third-party modules in the REPL by inheriting
module.paths from the REPL's parent module.

Commit ee72ee75 ("module,repl: remove repl require() hack") introduced
a regression where require() of modules in node_modules directories
no longer worked in the REPL (and fortunately only in the REPL.)
It turns out we didn't have test coverage for that but we do now.

Fixes: https://github.com/nodejs/node/issues/4208
PR-URL: https://github.com/nodejs/node/pull/4215


Reviewed-By: Roman Reiss <me@silverwind.io>