unless we're backward compatible.

Have one bigger lisp script to replace several shell scripts.

A system named foo/bar will be looked up in a registered file foo.asd.
This makes it possible to sensibly name several systems in a .asd file
and still have asdf find them all by name.
We now use it to not have the asdf header be part of asdf-driver.

A new generic operation build-op makes it possible to deal with
the fact that the default operation for systems need not be load-op,
yet that the end-user does not want to have to know the exact operation
for each of the system he uses.

ensure-pathname has been improved again, and its clients tweaked.

remove-keys was made more sensible by using EQL rather than STRING-EQUAL.

:version need not take the first form in a file, but can take
a path to a subform. This makes it possible to get the exact subform
in a Lisp source file that has the string.
See SUB-OBJECT for how these paths work.

Cleanup of the semantics of ENSURE-FUNCTION on CONSes: use APPLY, not EVAL.

Move things around and rename functions to improve backward compatibility.
The driver now has its own backward-compatibility file.

* Pathname support has been cleaned up, yet again,
 extending and renaming COERCE-PATHNAME into PARSE-UNIX-NAMESTRING,
 also ENSURE-PATHNAME, many docstrings, and plenty of small enhancements.
* Bundles were refactored to take advantage of the new, more sensible,
 component-depends-on semantics.
* Image support was cleaned up again, and program-op was implemented
 to produce a standalone executable on supported platforms;
 a working hello-world-example is included amongst tests.
* The *compile-file-function* indirection was removed, with the
 ECL and MKCL object file support
 being folded into compile-file* instead.
* systems now can have NIL as component-pathname,
 instead of providing a non-sensible bogus pathname
 when no sensible pathname was determined.
 Most of our pathname functions have sensible default behavior
 when provided NIL instead of a pathname as an argument.

Also, improve the bump-version script.

* Fix bug found by CLISP regarding improper wildening.
* On CLISP, avoid nicknames in the package-definition-form.
* For ABCL avoid (a . #+foo b) pattern
* Also, test-clean-load now works on all lisps, not just SBCL

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.

The general-purpose support code is now
a bit less than 50% of the code in ASDF.

This notably includes the former xcvb-driver:run-program/,
a much better replacement for run-shell-command.
This also includes image initialization, dumping, quitting.

Make default-directory a root pathname, remove it from source-registry.
Have it use lisp-implementation-directory.
Remove any attempt to use the "current directory".
Users who want that can still try to
	(pushnew '*default-pathname-defaults* asdf:*central-registry*)

Rename tmp/ to build/ and move asdf.lisp there. Update asdf.asd.
Rename implementation.lisp to compatibility.lisp.
Move *asdf-verbose* and asdf-message to upgrade.lisp

New pathname functions to work around more logical-pathname issues.
See discussion with rpgoldman on asdf-devel, and see CCL ticket:953.
Also, tweak build to reflect recent refactoring of asdf.
WIP of define-package work needed for clean upgrade (still broken).

TODO: Create a define-package that can make it upgrade itself.

ECL output-files semantics has changed, so unintern the old one rather than conflict.
Rename *compile-op-compile-file-function* to just *compile-file-function*.
Factor all the lisp build perform's through perform-lisp-FOO,
so they can be shared with concatenated targets that are not cl-source-file
without fighting default methods and class inheritance.

Introduce a PLAN object for dependency traversal;
have component visit functions use it instead of the ancestor operation.
Introduce an explicit ACTION-STATUS class.
Introduce a PLAN-RECORD-DEPENDENCY hook for POIU.

Also hush warnings around upgrade-only methods.
More uniformly redirect output during testing.

If/when XCL ever resurrects, it's time to further maintain its support.

Be more selective in what warnings get quashed when upgrading ASDF.
Skip bundle test on ABCL, ECL-bytecodes.
Sleep more in test1.

Found this bug during ASDF upgrade tests.
Add ecl_bytecodes to the upgrade test regimes.
Rename it from ecl-bytecodes to work with stupid Bourne shell.
Add xcl to test regime.

Also added allegromodern to the testing regime,
after I found the recipe to create mlisp:
http://www.franz.com/support/faq/#s3q7

Change declare ignore to ignorable to make ACL happier.
Remove slot for if-component-dep-fails.
Update some tests and workaround a failure on ecl-bytecodes.

* Refactor load-system to use *load-system-operation*,
and change require-system and module-provide-asdf to use that.
* Remove broken-fasl-support: first, cormanlisp is supposed to have fixed it;
 second, cormanlisp is dead;
 third, one can now (setf *load-system-operation* 'load-source-op) instead.
* Reindent default-source-registry
* Fix a test in light of some previous package frobbing.

Don't upgrade ccl or cmucl on older asdf's due to incompatibilities.
Shouldn't matter since they already ship with more recent versions of asdf.

following discussion with Nikodemus on asdf-devel.
Also, improve the way we test for upgrade.
Disable upgrade test on cmucl from asdf 2.00*.
Restore -i.bak flag in bump-version: it's actually needed.

by using unintern rather than fmakunbound for redefined generic functions.