* More but still incomplete support for mkcl and cormanlisp.

Also, fix Makefile.release on a Mac.

This allows the examples to be created without having to install
an XCVB. The primary implementation is in bootstrap.lisp and
additional code in driver.lisp.
+ The created XCVB is made with one of the supported lisp
implementations even though the enclosing lisp invocation might
not be.
+ Refactored lisp-invocation into its own package.
+ The cache-description file contains notes about how the cache
should function. The cache is both the multi-user cache as in
distcc, ccache, etc, but also the user specific workspace for
where to dump fasl files and whatnot.

* Use define-command to define and register a command
* Introduce the notion of workspace to store intermediate and target files.
* Update Makefiles for new intended output paths

Fix a few glaring recent bugs.

* extract fasl type from target:
 at least lispworks depends on pathname type and its fasl type varies!
* rucksack not available on clisp (and needed fixes; see our xcvb repo of it)
* accept compile-file failure semantics of clisp
* suppress duplicate entries for a directory in the source-registry:
 The first one wins, with its recurse and exclude flags.
* fix hello and test/runme
* fix various option parsing mistakes

Extract version from git when finalizing the image (requires cl-launch 3.009).
On CCL/windows, work around bug ccl bug 858 in run-program.
Simplify some tests for run-program, fix others.

Extract version from git when finalizing the image (requires cl-launch 3.009).
On CCL/windows, work around bug ccl bug 858 in run-program.
Simplify some tests for run-program, fix others.

Try to make it work with gcl - but gcl fails to compile driver.lisp.

	settings known to xcvb or the individual value of a single one.
Change the default object-directory location to be
	$HOME/.cache/xcvb/common-lisp/<lisp-implementation-version>/
Added format! in driver.lisp to help with debugging and forcing output.
Debugged CMUCL support in driver.
Fixed implementation-identifier support in extract-target-properties.
Allowed Makefile in example-1 to parameterize on lisp implementation.
Refactored how option-specs are specified for command line options.
Removed dead code paths from simple-build backend that dealt with
	"xcvb.mk" and the makefile output file.
Muffled warnings when loading asdf.
Added target-asdf-version setting which you can query with show-settings.
Started DONE.rest

Conditionalize away the xcvb farmer to not depend on iolib.

We were using CCL's run-program, that spawned a thread that reset the
pthread_sigmask. Evil. We now use a run-program/process-output-stream
based on iolib and short-circuit the implementation's. Sigh.

Also, supersede some sbcl contrib asdf systems with appropriate requires.

* fix various bugs left over from .507.
* back out generation of Lisp files in object tree
 until we can provide build processes with a mapping from name to pathname.
* pass self-test.

Add (but not use yet) a pure grain set implementation.

* Introduce the world-grain abstraction as a step towards a farmer.
* A few important cleanups and refactorings.
* better hush the build