Fix build with opaque DH in LibreSSL 3.5.

Index: librtmp/dh.h
--- librtmp/dh.h.orig
+++ librtmp/dh.h
@@ -249,27 +249,31 @@ DHInit(int nKeyBits)
 {
   size_t res;
   MDH *dh = MDH_new();
+  MP_t p = NULL, g = NULL;
 
   if (!dh)
     goto failed;
 
-  MP_new(dh->g);
+  MP_new(g);
 
-  if (!dh->g)
+  if (!g)
     goto failed;
 
-  MP_gethex(dh->p, P1024, res);	/* prime P1024, see dhgroups.h */
+  MP_gethex(p, P1024, res);	/* prime P1024, see dhgroups.h */
   if (!res)
     {
       goto failed;
     }
 
-  MP_set_w(dh->g, 2);	/* base 2 */
+  MP_set_w(g, 2);	/* base 2 */
+  DH_set0_pqg(dh, p, NULL, g);
+  DH_set_length(dh, nKeyBits);
 
-  dh->length = nKeyBits;
   return dh;
 
 failed:
+  MP_free(g);
+  MP_free(p);
   if (dh)
     MDH_free(dh);
 
@@ -293,12 +297,10 @@ DHGenerateKey(MDH *dh)
       MP_gethex(q1, Q1024, res);
       assert(res);
 
-      res = isValidPublicKey(dh->pub_key, dh->p, q1);
+      res = isValidPublicKey((MP_t)DH_get0_pub_key(dh), (MP_t)DH_get0_p(dh), q1);
       if (!res)
 	{
-	  MP_free(dh->pub_key);
-	  MP_free(dh->priv_key);
-	  dh->pub_key = dh->priv_key = 0;
+          return 0;
 	}
 
       MP_free(q1);
@@ -314,15 +316,15 @@ static int
 DHGetPublicKey(MDH *dh, uint8_t *pubkey, size_t nPubkeyLen)
 {
   int len;
-  if (!dh || !dh->pub_key)
+  if (!dh || !DH_get0_pub_key(dh))
     return 0;
 
-  len = MP_bytes(dh->pub_key);
+  len = MP_bytes(DH_get0_pub_key(dh));
   if (len <= 0 || len > (int) nPubkeyLen)
     return 0;
 
   memset(pubkey, 0, nPubkeyLen);
-  MP_setbin(dh->pub_key, pubkey + (nPubkeyLen - len), len);
+  MP_setbin(DH_get0_pub_key(dh), pubkey + (nPubkeyLen - len), len);
   return 1;
 }
 
@@ -364,7 +366,7 @@ DHComputeSharedSecretKey(MDH *dh, uint8_t *pubkey, siz
   MP_gethex(q1, Q1024, len);
   assert(len);
 
-  if (isValidPublicKey(pubkeyBn, dh->p, q1))
+  if (isValidPublicKey(pubkeyBn, (MP_t)DH_get0_p(dh), q1))
     res = MDH_compute_key(secret, nPubkeyLen, pubkeyBn, dh);
   else
     res = -1;