module: cache regular expressions

None of these regular expressions will change, so there is no need to
generate them every time in hot code paths.

Provides a small performance improvement in module loading. (5-10%)

PR-URL: https://github.com/nodejs/node/pull/3869


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>