[asdf-devel] logical pathname fixes

I added a more functional test for logical pathnames, and made a round of fixes for logical pathnames. Some things are still broken on CLISP and Allegro, but I blame the implementations (see test/test-logical-pathname.script for details).

p-cos, janderson, pjb: I believe you are the three known users of logical pathnames. Can you test the latest ASDF in your respective setups? (currently 2.20.10).

—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org Think you can, or think you can't — either way, you'll be right. — Henry Ford