BUG/MEDIUM: ssl: Don't attempt to use early data with libressl.

Libressl doesn't yet provide early data, so don't put the CO_FL_EARLY_SSL_HS
on the connection if we're building with libressl, or the handshake will
never be done.
diff --git a/src/backend.c b/src/backend.c
index ae704de..5807a2e 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1582,7 +1582,9 @@
 	}
 
 
-#ifdef USE_OPENSSL
+#if USE_OPENSSL && (defined(OPENSSL_IS_BORINGSSL) || \
+    ((OPENSSL_VERSION_NUMBER >= 0x10101000L) && !defined(LIBRESSL_VERSION_NUMBER)))
+
 	if (!reuse && cli_conn && srv &&
 	    (srv->ssl_ctx.options & SRV_SSL_O_EARLY_DATA) &&
 	    /* Only attempt to use early data if either the client sent