Merge pull request #6 from thecabinet/master

cleanup of nqp::sha1; implement nqp::exit and nqp::sleep
arnsholt++ did this task.
makefile clean
Compile QAST::WVal.

Note that there's no SC support yet so it doesn't actually work when
run. However, since compiling attribute access depends on it, it was
obscuring the many other things that need work in nqp-mo.pm.