actually implement "fixing letrec"

* module/Makefile.am (SOURCES): Reorganize so GHIL is compiled last,
  along with ecmascript.

* module/language/scheme/spec.scm: Remove references to GHIL, as it's
  bitrotten and obsolete..

* module/language/tree-il.scm (make-tree-il-folder): Rework so that we
  only have down and up procs, and call down and up on each element.
* module/language/tree-il/analyze.scm (analyze-lexicals): Fix a thinko
  handling let-values.

* module/language/tree-il/fix-letrec.scm: Actually implement fixing
  letrec. The resulting code will perform better, but violations of the
  letrec restriction are not detected. This behavior is allowed by the
  spec, but it is undesirable. Perhaps that will be fixed later.

* module/language/tree-il/inline.scm (inline!): Fix a case in which
  ((lambda args foo)) would be erroneously inlined to foo. Remove empty
  let, letrec, and fix statements.

* module/language/tree-il/primitives.scm (effect-free-primitive?): New
  public predicate.

module/language/scheme/spec.scm

@@ -1,6 +1,6 @@
 ;;; Guile Scheme specification
 
-;; Copyright (C) 2001 Free Software Foundation, Inc.
+;; Copyright (C) 2001, 2009 Free Software Foundation, Inc.
 
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -20,7 +20,6 @@
 
 (define-module (language scheme spec)
   #:use-module (system base language)
-  #:use-module (language scheme compile-ghil)
   #:use-module (language scheme compile-tree-il)
   #:use-module (language scheme decompile-tree-il)
   #:export (scheme))
@@ -39,8 +38,7 @@
   #:title	"Guile Scheme"
   #:version	"0.5"
   #:reader	read
-  #:compilers   `((tree-il . ,compile-tree-il)
-                  (ghil . ,compile-ghil))
+  #:compilers   `((tree-il . ,compile-tree-il))
   #:decompilers `((tree-il . ,decompile-tree-il))
   #:evaluator	(lambda (x module) (primitive-eval x))
   #:printer	write