Fix build with opaque structs in LibreSSL 3.5

Index: src/lib/crypt_ops/crypto_rsa_openssl.c
--- src/lib/crypt_ops/crypto_rsa_openssl.c.orig
+++ src/lib/crypt_ops/crypto_rsa_openssl.c
@@ -47,7 +47,7 @@ struct crypto_pk_t
 int
 crypto_pk_key_is_private(const crypto_pk_t *k)
 {
-#ifdef OPENSSL_1_1_API
+#if defined(OPENSSL_1_1_API) || defined(LIBRESSL_VERSION_NUMBER)
   if (!k || !k->key)
     return 0;
 
@@ -212,7 +212,7 @@ crypto_pk_public_exponent_ok(const crypto_pk_t *env)
 
   const BIGNUM *e;
 
-#ifdef OPENSSL_1_1_API
+#if defined(OPENSSL_1_1_API) || defined(LIBRESSL_VERSION_NUMBER)
   const BIGNUM *n, *d;
   RSA_get0_key(env->key, &n, &e, &d);
 #else
@@ -242,7 +242,7 @@ crypto_pk_cmp_keys(const crypto_pk_t *a, const crypto_
   const BIGNUM *a_n, *a_e;
   const BIGNUM *b_n, *b_e;
 
-#ifdef OPENSSL_1_1_API
+#if defined(OPENSSL_1_1_API) || defined(LIBRESSL_VERSION_NUMBER)
   const BIGNUM *a_d, *b_d;
   RSA_get0_key(a->key, &a_n, &a_e, &a_d);
   RSA_get0_key(b->key, &b_n, &b_e, &b_d);
@@ -279,7 +279,7 @@ crypto_pk_num_bits(crypto_pk_t *env)
   tor_assert(env);
   tor_assert(env->key);
 
-#ifdef OPENSSL_1_1_API
+#if defined(OPENSSL_1_1_API) || defined(LIBRESSL_VERSION_NUMBER)
   /* It's so stupid that there's no other way to check that n is valid
    * before calling RSA_bits().
    */
@@ -572,7 +572,7 @@ static bool
 rsa_private_key_too_long(RSA *rsa, int max_bits)
 {
   const BIGNUM *n, *e, *p, *q, *d, *dmp1, *dmq1, *iqmp;
-#ifdef OPENSSL_1_1_API
+#if defined(OPENSSL_1_1_API) || defined(LIBRESSL_VERSION_NUMBER)
 
 #if OPENSSL_VERSION_NUMBER >= OPENSSL_V_SERIES(1,1,1)
   n = RSA_get0_n(rsa);