linked-list: Change return value of find_first() and signature of its callback

This avoids the unportable five pointer hack.

src/libstrongswan/credentials/credential_manager.c

@@ -812,11 +812,12 @@ static bool verify_trust_chain(private_credential_manager_t *this,
 	return trusted;
 }
 
-/**
- * List find match function for certificates
- */
-static bool cert_equals(certificate_t *a, certificate_t *b)
+CALLBACK(cert_equals, bool,
+	certificate_t *a, va_list args)
 {
+	certificate_t *b;
+
+	VA_ARGS_VGET(args, b);
 	return a->equals(a, b);
 }
 
@@ -896,8 +897,7 @@ METHOD(enumerator_t, trusted_enumerate, bool,
 			continue;
 		}
 
-		if (this->failed->find_first(this->failed, (void*)cert_equals,
-									 NULL, current) == SUCCESS)
+		if (this->failed->find_first(this->failed, cert_equals, NULL, current))
 		{	/* check each candidate only once */
 			continue;
 		}

src/libstrongswan/credentials/sets/mem_cred.c

@@ -149,8 +149,12 @@ METHOD(credential_set_t, create_cert_enumerator, enumerator_t*,
 									cert_data_destroy);
 }
 
-static bool certificate_equals(certificate_t *item, certificate_t *cert)
+CALLBACK(certificate_equals, bool,
+	certificate_t *item, va_list args)
 {
+	certificate_t *cert;
+
+	VA_ARGS_VGET(args, cert);
 	return item->equals(item, cert);
 }
 
@@ -163,9 +167,8 @@ static certificate_t *add_cert_internal(private_mem_cred_t *this, bool trusted,
 {
 	certificate_t *cached;
 	this->lock->write_lock(this->lock);
-	if (this->untrusted->find_first(this->untrusted,
-									(linked_list_match_t)certificate_equals,
-									(void**)&cached, cert) == SUCCESS)
+	if (this->untrusted->find_first(this->untrusted, certificate_equals,
+									(void**)&cached, cert))
 	{
 		cert->destroy(cert);
 		cert = cached->get_ref(cached);
@@ -201,9 +204,8 @@ METHOD(mem_cred_t, get_cert_ref, certificate_t*,
 	certificate_t *cached;
 
 	this->lock->read_lock(this->lock);
-	if (this->untrusted->find_first(this->untrusted,
-									(linked_list_match_t)certificate_equals,
-									(void**)&cached, cert) == SUCCESS)
+	if (this->untrusted->find_first(this->untrusted, certificate_equals,
+									(void**)&cached, cert))
 	{
 		cert->destroy(cert);
 		cert = cached->get_ref(cached);