siphash24: introduce siphash24_compress_typesafe() macro

To prevent copy-and-paste mistake.

This also introduce in_addr_hash_func().

No functional change, just refactoring.

src/basic/in-addr-util.h

@@ -185,6 +185,7 @@ static inline size_t FAMILY_ADDRESS_SIZE(int family) {
  * See also oss-fuzz#11344. */
 #define IN_ADDR_NULL ((union in_addr_union) { .in6 = {} })
 
+void in_addr_hash_func(const union in_addr_union *u, int family, struct siphash *state);
 void in_addr_data_hash_func(const struct in_addr_data *a, struct siphash *state);
 int in_addr_data_compare_func(const struct in_addr_data *x, const struct in_addr_data *y);
 void in6_addr_hash_func(const struct in6_addr *addr, struct siphash *state);