Handle exit codes when running from the Lisp REPL.
Driver tweaks; notably control conditions when loading an ASDF system.

* 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

Fixes to the bridge and to CMUCL, ECL, SCL support that make it work better.

The latter is a GNUism, the former is there on BSD (including MacOS X), too.
Also, adjust the ssr test to match the new ssr output format.

Fix a few glaring recent bugs.

c::builder'ing shared libraries.  Refactored the grain class hierarchy
a bit.

+ Partial changes to get xcvb to build a binary of xcvb.
+ Extending :create-image to support executables.
+ Support for command line arguments when resuming the executable.
  These are passed to the entry-point. However, each lisp vendor
  mangles the argv a little and it needs work to be really right.
  For now it is good enough.
+ dump-image for ecl got hacked upon, but it is currently broken.
+ Changed example-1 to produce an executable, but currently this
  only works for lisp implementations which can produce them. This
  needs more consideration in the future, for example, the
  "executable" could be a script which invokes an image.
+ simple-build can now accept targets with empty computations.
  This implements the "phony target" idea in simple-build.

* 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.

when emitting output so it looks nice on the screen.
Added much more instrumentation of what xcvb isdoing at verbosity 10.
Got rid of some commented out code we don't need.

	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

need to deal better with the configure.mk file. Should it ultimately
just be in this directory? What's the policy for the configure.mk
file--need to figure it out.

Added new unit test for slurping lines with an empty input.
Changed how TMP is used on unix in the call-with-temporary-file macro.