Add cl-getopt

cl-getopt (https://github.com/ghollisjr/cl-getopt) is a CFFI wrapper to the libc "getopt_long" function.

There's already a "getopt" project in quicklisp, but that library is a new implementation in Lisp and is not fully compatible with the libc implementation.

This library is guaranteed to be fully compatible as it's just a CFFI wrapper.