Some doc & test frobbing.

Rename RUN-PROGRAM/ to RUN-PROGRAM.
Can't export it from ASDF because it causes a clash in SB-GROVEL.

Rename SUB-OBJECT and :PATH to ACCESS-AT and :AT.

Get rid of TRANSLATE-OUTPUT-P.
Instead, check whether the component's BUILD-OPERATION
is the same as the current operation.

Also, make script re-loadable in a debug session.

Don't key upgrade attempt on source-registry, since things can also change
in the central-registry, etc.
Also rename required-files to direct-dependency-files
Improve the new convenience function pattern to work with operation initargs.
Implement getcwd on all platforms.
Actually catch sb-grovel messages.

Tests: make u l=ecl instead of make test-upgrade lisp=ecl
Tests: put the setup around the script, not inside;
Tests: start using globals, much easier for debugging

Package tweaks to make CLISP complain less.
run-program/ and run-shell-command fixes and test updates.
wildening fix to issue found by CLISP.
! is used by EXT on CLISP, so use !p for defparameter.
More pathname madness for allegro.
Better upgrade.

Tests: SBCL passes test-lisp and test-upgrade
Also:
* big refactoring of test infrastructure
* contrib/debug.lisp and (asdf/driver:asdf-debug) for debugging.
* remove aif and it, use the cleaner if-bind.
* backtrace support, with improvements from trivial-backtrace.
* integration of asdf-condition-control (originally from xcvb-driver)
* simplify the upgrade heuristic: always tries to upgrade once.
  The previous heuristic was too complex with too many failure cases.
  You are thus assumed to want a given version asdf
  if and only if it is in your source-registry.

Also, update testing infrastructure to work with latest xcl from git.

Also, use coerce-pathname in asdf-ecl and deprecate merge-component-name-type.

Attempt to use features to prevent running this script on Windows.
Checks Mac and POSIX positions of true and false.