Add async certificate verification callback.

This also serves as a certificate verification callback for
CRYPTO_BUFFER-based consumers. Remove the silly
SSL_CTX_i_promise_to_verify_certs_after_the_handshake placeholder.

Bug: 54, chromium:347402
Change-Id: I4c6b445cb9cd7204218acb2e5d1625e6f37aff6f
Reviewed-on: https://boringssl-review.googlesource.com/17964
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/ssl/ssl_test.cc b/ssl/ssl_test.cc
index 2c648ac..640718a 100644
--- a/ssl/ssl_test.cc
+++ b/ssl/ssl_test.cc
@@ -3276,7 +3276,11 @@
   ASSERT_TRUE(SSL_CTX_set_chain_and_key(server_ctx.get(), &chain[0],
                                         chain.size(), key.get(), nullptr));
 
-  SSL_CTX_i_promise_to_verify_certs_after_the_handshake(client_ctx.get());
+  SSL_CTX_set_custom_verify(
+      client_ctx.get(), SSL_VERIFY_PEER,
+      [](SSL *ssl, uint8_t *out_alert) -> ssl_verify_result_t {
+        return ssl_verify_ok;
+      });
 
   bssl::UniquePtr<SSL> client, server;
   ASSERT_TRUE(ConnectClientAndServer(&client, &server, client_ctx.get(),