fix bug in self-tail-recursion with "external" variables; other sundries

* gdbinit (pp, inst): New commands.

* libguile/vm-engine.c (vm_error_not_a_pair): New error case.

* libguile/vm-i-scheme.c (VM_VALIDATE_CONS): New macro -- use this
  instead of SCM_VALIDATE_* because SCM_VALIDATE will exit nonlocally
  before we have a chance to sync the regs.
  (car, cdr, set-car, set-cdr): Use VM_VALIDATE_CONS.

* libguile/vm-i-system.c (goto/args): Bugfix: when doing a
  self-tail-recursion, allocate fresh externals. Fixes use of match.go.

* module/system/vm/assemble.scm (dump-object!): Add some checks that we
  aren't dumping out values that the VM can't handle.

* module/system/vm/disasm.scm (disassemble-externals): Fix rotten call to
  `print-info'.

* oop/goops/dispatch.scm: Add a FIXME.

* testsuite/Makefile.am (vm_test_files):
* testsuite/t-closure4.scm (extract-symbols): New test, distilled with
  much effort out of match.scm.

* ice-9/Makefile.am (NOCOMP_SOURCES): Re-enable compilation of match.scm.
  Yay!

module/system/vm/assemble.scm

@@ -355,6 +355,11 @@
 		(push-code! `(make-int16 ,(ash x -8) ,(logand x (1- (ash 1 8)))))))
 	     (else
 	      ;; Other cases
+              (if (> (+ nargs nlocs) 255)
+                  (error "too many locals" nargs nlocs))
+              ;; really it should be a flag..
+              (if (> nrest 1) (error "nrest should be 0 or 1" nrest))
+              (if (> next 255) (error "too many externals" next))
 	      (push-code! (object->code nargs))
 	      (push-code! (object->code nrest))
 	      (push-code! (object->code nlocs))

module/system/vm/disasm.scm

@@ -109,7 +109,7 @@
     (do ((n 0 (1+ n))
 	 (l exts (cdr l)))
 	((null? l) (newline))
-      (print-info n (car l) #f))))
+      (print-info n (car l) #f #f))))
 
 (define-macro (unless test . body)
   `(if (not ,test) (begin ,@body)))