2.017.11: Fix run-shell-command on allegro/unix, tweak it on Windows:

break things differently, giving user more control when things break.
Document somewhat the mess that is asdf:run-shell-command, and
recommend xcvb-driver:run-program/process-output-stream as a replacement.
Also, rename some testing targets in the Makefile, update testing status.
Finally, hush cmucl.