One key was to use
 (define-compiled-dependency :build (x) `(:build ,x))
instead of `(:compile-build ,x)
because e.g. asdf, cl-ppcre, etc., are often being fully used at compile-time
not just compiled against for use at run-time.

transient threads created by posix_spawn. Sigh.

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

change SBCL_HOME unsetting to be less uniform but more portable.
Fix posix-wait in CLISP as in the recent POIU fix.
My, we need a regression test suite!

* start some test infrastructure for release
* make image mode the default in configure.mk, for the sake of CCL
* fix the forker package, bake a collection macro
* extract executable and image name from target lisp (when possible)
 in view of tthsum'ing it in the future.

* now that we have individual :build-depends-on, more the forker outside of the driver.
* don't catch all serious-condition's (including process-reset), only errors.
* don't try to always create a standalone image (for now) as cl-launch doesn't know
 how to do it with CCL (yet).

* Move forker contents to driver. Think about farmer.
* doc update.

* start of a forker and farmer
* better error message when you forget to make your dependencies a list
* doc update