Functionify a macro.

Add TODO item.

Add print-object infrastructure for constituents (used while debugging).

Take advantage of recent ASDF 1.367 enhancements in pathname computation, when available.

Don't normalize away last component in a component name that has dots.

Note: previous commit to u-defpackage was unrelated to specified message.

Functionalize a few macros,
make constituent designators slightly more readable,
fix a typo,
fix a compiler warning in a test.