Fix a compile warning on OSX 10.6

src/common/address.c

@@ -311,7 +311,7 @@ tor_addr_is_internal(const tor_addr_t *addr, int for_listening)
  *  brackets.
  */
 const char *
-tor_addr_to_str(char *dest, const tor_addr_t *addr, int len, int decorate)
+tor_addr_to_str(char *dest, const tor_addr_t *addr, size_t len, int decorate)
 {
   const char *ptr;
   tor_assert(addr && dest);

src/common/address.h

@@ -144,7 +144,7 @@ int tor_addr_port_parse(const char *s, tor_addr_t *addr_out,
 int tor_addr_parse_mask_ports(const char *s,
                               tor_addr_t *addr_out, maskbits_t *mask_out,
                               uint16_t *port_min_out, uint16_t *port_max_out);
-const char * tor_addr_to_str(char *dest, const tor_addr_t *addr, int len,
+const char * tor_addr_to_str(char *dest, const tor_addr_t *addr, size_t len,
                              int decorate);
 int tor_addr_from_str(tor_addr_t *addr, const char *src);
 void tor_addr_copy(tor_addr_t *dest, const tor_addr_t *src);