Adjust GC_debug_malloc/realloc_replacement macro to match the API fun…

…ction

* malloc.c (GC_debug_malloc_replacement): Pass NULL (instead of
"unknown") to "s" argument of GC_debug_malloc to match that
replacement definition in dbg_mlc.c.
* mallocx.c (GC_debug_realloc_replacement): Likewise.

malloc.c

@@ -355,9 +355,8 @@ GC_API void * GC_CALL GC_malloc_uncollectable(size_t lb)
 /* malloc replacements.  Otherwise we end up saving a                   */
 /* meaningless return address in the object.  It also speeds things up, */
 /* but it is admittedly quite ugly.                                     */
-
 # define GC_debug_malloc_replacement(lb) \
-                        GC_debug_malloc(lb, GC_DBG_RA "unknown", 0)
+                        GC_debug_malloc(lb, GC_DBG_RA NULL, 0)
 
 void * malloc(size_t lb)
 {

mallocx.c

@@ -153,9 +153,8 @@ GC_API void * GC_CALL GC_realloc(void * p, size_t lb)
 # ifdef REDIRECT_REALLOC
 
 /* As with malloc, avoid two levels of extra calls here.        */
-
 # define GC_debug_realloc_replacement(p, lb) \
-        GC_debug_realloc(p, lb, GC_DBG_RA "unknown", 0)
+        GC_debug_realloc(p, lb, GC_DBG_RA NULL, 0)
 
 void * realloc(void * p, size_t lb)
   {