antithread: update example Makefile and arabella example.

ccan/antithread/examples/Makefile

-CFLAGS=-g -O3 -Wall -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations -I../../..
+CFLAGS=-g -Wall -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations -I../../.. ../../talloc.o ../../alloc.o ../../noerr.o ../../read_write_all.o ../../antithread.o # -O3
+LDLIBS=-ljpeg -lm
 
-all: dns_lookup
+all: dns_lookup arabella
 
-dns_lookup: dns_lookup.c ../../../libccan.a
-	$(CC) $(CFLAGS) -o $@ $^
-
-arabella: arabella.c ../../../libccan.a
-	$(CC) $(CFLAGS) -o $@ $^ -ljpeg -lm
+clean:
+	rm -f dns_lookup arabella

ccan/antithread/examples/arabella.c

@@ -377,7 +377,7 @@ static struct drawing *breed_drawing(const void *ctx,
 
 /* This is our anti-thread.  It does the time-consuming operation of
  * breeding two drawings together and scoring the result. */
-static void *breeder(struct at_pool *atp, const struct image *master)
+static void *breeder(struct at_pool *atp, struct image *master)
 {
 	const struct drawing *a, *b;