Rewrite the X509->alert mapping code

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5780)
diff --git a/ssl/statem/statem_clnt.c b/ssl/statem/statem_clnt.c
index 29db4bc..91b986f 100644
--- a/ssl/statem/statem_clnt.c
+++ b/ssl/statem/statem_clnt.c
@@ -1898,7 +1898,7 @@
      * set. The *documented* interface remains the same.
      */
     if (s->verify_mode != SSL_VERIFY_NONE && i <= 0) {
-        SSLfatal(s, ssl_verify_alarm_type(s->verify_result),
+        SSLfatal(s, ssl_x509err2alert(s->verify_result),
                  SSL_F_TLS_PROCESS_SERVER_CERTIFICATE,
                  SSL_R_CERTIFICATE_VERIFY_FAILED);
         goto err;