Implment nqp::{mkdir, rmdir, chdir}.

Raise an error when an op receives to much arguments.
A stub nqp::getcomp('nqp') to make nqp::getcomp('nqp').backend.name work.
Pass test 63, work towards passing 78.

Implement cwd, shell, getenvhash ops.
Put a bunch of subs into the mini setting.
Fix bug.
Pass test 37.

Support slurpy named parameters.
Remove debug statements.