Add support for SLE-15.

OBS-URL: https://build.opensuse.org/package/show/network/vsftpd?expand=0&rev=164

disable-tls13-to-support-older-openssl-versions.patch

@@ -0,0 +1,14 @@
+Index: vsftpd-3.0.5/ssl.c
+===================================================================
+--- vsftpd-3.0.5.orig/ssl.c
++++ vsftpd-3.0.5/ssl.c
+@@ -95,7 +95,9 @@ ssl_init(struct vsf_session* p_sess)
+     }
+     if (!tunable_tlsv1_3)
+     {
++#ifdef SSL_OP_NO_TLSv1_3
+       options |= SSL_OP_NO_TLSv1_3;
++#endif
+     }
+     SSL_CTX_set_options(p_ctx, options);
+     if (tunable_rsa_cert_file)