Add encoded points to other EC curves too.

Add encoded point ctrl support for other curves: this makes it possible
to handle X25519 and other EC curve point encoding in a similar way
for TLS.
Reviewed-by: NRich Salz <rsalz@openssl.org>

crypto/ec/ec_ameth.c

@@ -496,6 +496,13 @@ static int ec_pkey_ctrl(EVP_PKEY *pkey, int op, long arg1, void *arg2)
         *(int *)arg2 = NID_sha256;
         return 2;
 
+    case ASN1_PKEY_CTRL_SET1_TLS_ENCPT:
+        return EC_KEY_oct2key(EVP_PKEY_get0_EC_KEY(pkey), arg2, arg1, NULL);
+
+    case ASN1_PKEY_CTRL_GET1_TLS_ENCPT:
+        return EC_KEY_key2buf(EVP_PKEY_get0_EC_KEY(pkey),
+                              POINT_CONVERSION_UNCOMPRESSED, arg2, NULL);
+
     default:
         return -2;