minor SCM_DEBUG patch

[Ken Raeburn <raeburn@raeburn.org>]

The SCM_GC_MARK_P macro doesn't exist any more, but is still mentioned  
in a few places.  With SCM_DEBUG defined, one of them actually gets  
compiled.  While looking at this, I also noticed three macros in  
deprecated.h (which were there in 1.8) which use non-existent macros  
including SCM_GC_MARK_P, and deleted those too.  I didn't touch the  
other uses of SCM_GC_MARK_P in futures.c.

With this, and my pair-checking patches for objects.c and eval.i.c  
(sent September 5, still awaiting review from a developer familiar  
enough with the code), I can build a version with SCM_DEBUG that  
passes tests.

Related but not addressed here: Several places still check  
scm_gc_running_p and conditionally execute code (or not), but it's now  
defined as a macro always expanding to 0.

     Clean up some uses of old GC macros that don't exist any more.

     * libguile/deprecated.h (SCM_GC8MARKP, SCM_SETGC8MARK,  
SCM_CLRGC8MARK):
       Delete.
     * libguile/gc.c (scm_assert_cell_valid): Remove check of  
SCM_GC_MARK_P.

diff --git a/libguile/deprecated.h b/libguile/deprecated.h
index ed1a105..5680d09 100644
--- a/libguile/deprecated.h
+++ b/libguile/deprecated.h
@@ -120,9 +120,6 @@ SCM_DEPRECATED SCM scm_unprotect_object (SCM obj);
    (SCM_SETCDR ((x), SCM_PACK (SCM_UNPACK (SCM_CDR (x)) | (y))))
  #define SCM_FREEP(x) (0)
  #define SCM_NFREEP(x) (1)
-#define SCM_GC8MARKP(x) SCM_GC_MARK_P (x)
-#define SCM_SETGC8MARK(x) SCM_SET_GC_MARK (x)
-#define SCM_CLRGC8MARK(x) SCM_CLEAR_GC_MARK (x)
  #define SCM_GCTYP16(x) SCM_TYP16 (x)
  #define SCM_GCCDR(x) SCM_CDR (x)
  SCM_DEPRECATED void scm_remember (SCM * ptr);
diff --git a/libguile/gc.c b/libguile/gc.c
index 9c56d04..96e3c30 100644
--- a/libguile/gc.c
+++ b/libguile/gc.c
@@ -146,18 +146,7 @@ scm_assert_cell_valid (SCM cell)
        */
        if (scm_expensive_debug_cell_accesses_p)
  	scm_i_expensive_validation_check (cell);
-#if (SCM_DEBUG_MARKING_API == 0)
-      if (!SCM_GC_MARK_P (cell))
-	{
-	  fprintf (stderr,
-		   "scm_assert_cell_valid: this object is unmarked. \n"
-		   "It has been garbage-collected in the last GC run: "
-		   "%lux\n",
-                   (unsigned long) SCM_UNPACK (cell));
-	  abort ();
-	}
-#endif /* SCM_DEBUG_MARKING_API */
-
+
        scm_i_cell_validation_already_running = 0;  /* re-enable */
      }
  }