fix self tail recursion to different case-lambda clauses

http://savannah.gnu.org/bugs/?33362

* module/language/tree-il/compile-glil.scm (flatten-lambda-case): Rename
  from flatten, as it really just takes a particular case.  Instead of
  iteratively compiling lambda cases through `comp', tail-call through
  flatten-lambda-case.  This allows code to see which case it's being
  compiled in.  Take advantage of that to limit the self-tail-call
  optimization to self-calls to the same case -- otherwise we might be
  jumping to a label without having reserved the right number of
  locals.
  (flatten-lambda): Adapt the caller.

* test-suite/tests/compiler.test ("case-lambda"): Add a test.

test-suite/tests/compiler.test

@@ -1,5 +1,5 @@
 ;;;; compiler.test --- tests for the compiler      -*- scheme -*-
-;;;; Copyright (C) 2008, 2009, 2010 Free Software Foundation, Inc.
+;;;; Copyright (C) 2008, 2009, 2010, 2011 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
@@ -149,3 +149,18 @@
                                        ((y)   y)
                                        ((y z) (list y z)))))))
         (not (not (memv 0 (map source:addr s))))))))
+
+(with-test-prefix "case-lambda"
+  (pass-if "self recursion to different clause"
+    (equal? (with-output-to-string
+              (lambda ()
+                (let ()
+                  (define t
+                    (case-lambda
+                      ((x)
+                       (t x 'y))
+                      ((x y)
+                       (display (list x y))
+                       (list x y))))
+                  (display (t 'x)))))
+            "(x y)(x y)")))