lib: reduce process.binding() calls

This commit better handles calls to process.binding() in lib/ by
no longer lazy loading the bindings (the load times themselves are
rather miniscule compared to the load time of V8) and never reloading
the bindings (which is 172 times slower than referencing a variable with
the same value).

PR-URL: https://github.com/iojs/io.js/pull/1367


Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>