CONTRIB: merge ip6range with iprange

No need to have two separate sub-projects doing the same thing, let's
merge them.

contrib/ip6range/Makefile

@@ -1,13 +0,0 @@
-CC       = gcc
-OPTIMIZE = -O3
-LDFLAGS  = -s
-
-OBJS     = ip6range
-
-all: $(OBJS)
-
-%: %.c
-	$(CC) $(LDFLAGS) $(OPTIMIZE) -o $@ $^
-
-clean:
-	rm -f $(OBJS) *.o *.a *~

contrib/iprange/Makefile

@@ -1,8 +1,8 @@
-CC       = gcc
+CC       = cc
 OPTIMIZE = -O3
 LDFLAGS  = -s
 
-OBJS     = iprange
+OBJS     = iprange ip6range
 
 all: $(OBJS)
 

contrib/iprange/ip6range.c

@@ -314,7 +314,7 @@ static void usage(const char *argv0)
 		"\n", argv0);
 }
 
-main(int argc, char **argv)
+int main(int argc, char **argv)
 {
 	char line[MAXLINE];
 	int l, lnum;
@@ -393,4 +393,5 @@ main(int argc, char **argv)
 			convert_range(&sa, &da, he, NULL);
 		}
 	}
+	return 0;
 }