Remove broken attempt to compile libc's malloc source directly; this

allows this tool to compile again. Albeit, now to test a new malloc
implementation one has to install the new libc which may have bad
consequences (i.e. if the new malloc implementation were buggy).

Add logic to workaround malloc's current behaviour of returning an
invalid non-NULL pointer for 0 byte allocation requests; this prevents the
tool from coring during the NOPS loop.

Add $FreeBSD$ tags.

tools/test/malloc/Makefile

@@ -1,5 +1,6 @@
+# $FreeBSD$
 PROG=	malloc
-SRCS=	main.c malloc.c
+SRCS=	main.c
 .PATH:	${.CURDIR}/../../../lib/libc/stdlib
 
 NOMAN=	sorry

tools/test/malloc/main.c

@@ -1,3 +1,4 @@
+/* $FreeBSD$ */
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -19,7 +20,7 @@ main(int argc, char **argv)
     printf("BRK(0)=%x ",sbrk(0));
     foo = malloc (sizeof *foo * NBUCKETS);
     memset(foo,0,sizeof *foo * NBUCKETS);
-    for (i = 1; i <= 4096; i+=i) {
+    for (i = 1; i <= 4096; i *= 2) {
         for (j = 0 ; j < 40960/i && j < NBUCKETS; j++) {
 	    foo[j] = malloc(i);
         }
@@ -31,8 +32,15 @@ main(int argc, char **argv)
 
     for (i = 0 ; i < NOPS ; i++) {
 	j = random() % NBUCKETS;
-        k = random() % NSIZE;
+	k = random() % NSIZE;
 	foo[j] = realloc(foo[j], k & 1 ? 0 : k);
+	if (k & 1 || k == 0) {
+		/*
+		 * Workaround because realloc return bogus pointer rather than
+		 * NULL if passed zero length.
+		 */
+		foo[j] = 0;
+	}
 	if (foo[j])
 	    foo[j][0] = 1;
     }