Revert r1.9 and reinstate r1.6

The argument change to x5519_ge_scalarmult_base() was made to match the
prototype in the header. More recent compilers warn about such ptr vs
array mismatches.

lib/libcrypto/curve25519/curve25519.c

···
-/*	$OpenBSD: curve25519.c,v 1.14 2022/11/17 19:01:59 tb Exp $ */
+/*	$OpenBSD: curve25519.c,v 1.15 2023/04/02 15:36:53 tb Exp $ */
 /*
  * Copyright (c) 2015, Google Inc.
  *
···
  *
  * Preconditions:
  *   a[31] <= 127 */
-void x25519_ge_scalarmult_base(ge_p3 *h, const uint8_t *a) {
+void x25519_ge_scalarmult_base(ge_p3 *h, const uint8_t a[32]) {
   signed char e[64];
   signed char carry;
   ge_p1p1 r;