asdf 1.620: packaging updates
* rename ASDF-EXTENSIONS into ASDF-UTILITIES (keep the old as nickname) and update it to contain all the modern conveniences. * deprecate PATHNAME-SANS-NAME+TYPE, use PATHNAME-DIRECTORY-PATHNAME. * INITIALIZE-SOURCE-REGISTRY now takes an optional parameter that allows the user to provide his override. * Refactor PROCESS-SOURCE-REGISTRY and friends to make things more XCVB-ready. * Change optimize speed setting to 3 to prevent a weird compiler hang in SBCL at (speed 2) (debug 2) (safety 2).