Change tls_choose_sigalg so it can set errors and alerts.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2623)
diff --git a/ssl/ssl_err.c b/ssl/ssl_err.c
index ea5a763..cea6040 100644
--- a/ssl/ssl_err.c
+++ b/ssl/ssl_err.c
@@ -261,6 +261,7 @@
     {ERR_FUNC(SSL_F_TLS1_PRF), "tls1_PRF"},
     {ERR_FUNC(SSL_F_TLS1_SETUP_KEY_BLOCK), "tls1_setup_key_block"},
     {ERR_FUNC(SSL_F_TLS1_SET_SERVER_SIGALGS), "tls1_set_server_sigalgs"},
+    {ERR_FUNC(SSL_F_TLS_CHOOSE_SIGALG), "tls_choose_sigalg"},
     {ERR_FUNC(SSL_F_TLS_CLIENT_KEY_EXCHANGE_POST_WORK),
      "tls_client_key_exchange_post_work"},
     {ERR_FUNC(SSL_F_TLS_COLLECT_EXTENSIONS), "tls_collect_extensions"},