wiretap: don't use void parameter type in wtap_new_ipv6_callback_t

The wtap_new_ipv6_callback_t was initially introduced to allow
add_new_ipv6 to be called from the wiretap library. It's first parameter
is a 128-bit IPv6 address, so let's use that instead of a void pointer.

This fixes an UBSan error that could cause a crash when CFI is enabled:

    wiretap/wtap.c:1623:4: runtime error: call to function add_ipv6_name through pointer to incorrect function type 'void (*)(const void *, const char *, bool)'

Link: https://maskray.me/blog/2022-12-18-control-flow-integrity#fsanitizefunction

capinfos.c

@@ -1029,7 +1029,7 @@ count_ipv4_address(const unsigned int addr _U_, const char *name _U_, const bool
 }
 
 static void
-count_ipv6_address(const void *addrp _U_, const char *name _U_, const bool static_entry _U_)
+count_ipv6_address(const ws_in6_addr *addrp _U_, const char *name _U_, const bool static_entry _U_)
 {
     num_ipv6_addresses++;
 }

wiretap/wtap.c

@@ -1620,7 +1620,7 @@ wtapng_process_nrb_ipv6(wtap *wth, wtap_block_t nrb)
 	if (wth->add_new_ipv6) {
 		for (GList *elem = nrb_mand->ipv6_addr_list; elem != NULL; elem = elem->next) {
 			hashipv6_t *tp = elem->data;
-			wth->add_new_ipv6(tp->addr, tp->name, false);
+			wth->add_new_ipv6((ws_in6_addr *)tp->addr, tp->name, false);
 		}
 	}
 }

wiretap/wtap.h

@@ -1890,7 +1890,7 @@ typedef void (*wtap_new_ipv4_callback_t) (const unsigned addr, const char *name,
 WS_DLL_PUBLIC
 void wtap_set_cb_new_ipv4(wtap *wth, wtap_new_ipv4_callback_t add_new_ipv4);
 
-typedef void (*wtap_new_ipv6_callback_t) (const void *addrp, const char *name, const bool static_entry);
+typedef void (*wtap_new_ipv6_callback_t) (const ws_in6_addr *addrp, const char *name, const bool static_entry);
 WS_DLL_PUBLIC
 void wtap_set_cb_new_ipv6(wtap *wth, wtap_new_ipv6_callback_t add_new_ipv6);