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, move wild-modules to a contrib/ directory.
Refactor tests somewhat, introducing a function touch-file.

* Get rid of *stamp*, use lexical scoping everywhere
* Better handle non-filesystem actions in compute-action-stamp
* Have a simpler mechanism for backward compatibility with operation-done-p
* Have a more robust make-sub-operation, and use it where appropriate
* Test twiddling.

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

Add tests for configuration files.
Also export enable-asdf-binary-locations-compatibility.

be more clever about recompiling asdf.lisp,
and include implementation version in output-translations.

Examining the new TRAVERSE method definition, it became clear to me that
the current method would not propagate the value of the *forcing* special
variable properly.  The modification to the test-module-depend.{script,asd}
verifies this bug.

My module-dependency test had strayed from the other tests.

This test checks to see if a file in a module will be recompiled if a file
it depends on changes.  In "classic" asdf this does not happen --- it's
launchpad bug https://bugs.launchpad.net/asdf/+bug/502946

This is just a test for the condition.  The test fails in the current state
of ASDF.