Remove unused macro.
diff --git a/pigz.c b/pigz.c
index 8df8b75..b67e42e 100644
--- a/pigz.c
+++ b/pigz.c
@@ -655,7 +655,6 @@
     free_track(opaque, address);
 }
 
-#define MALLOC(s) malloc_track(&mem_track, s)
 #define REALLOC(p, s) realloc_track(&mem_track, p, s)
 #define FREE(p) free_track(&mem_track, p)
 #define OPAQUE (&mem_track)
@@ -664,7 +663,6 @@
 
 #else /* !PIGZ_DEBUG */
 
-#define MALLOC malloc
 #define REALLOC realloc
 #define FREE free
 #define OPAQUE Z_NULL