const correctness fixes for OpenSSL 4

Index: tls_ocsp.c
--- tls_ocsp.c.orig
+++ tls_ocsp.c
@@ -130,7 +130,7 @@ static OCSP_CERTID *
 tls_ocsp_get_certid(X509 *main_cert, STACK_OF(X509) *extra_certs,
     SSL_CTX *ssl_ctx)
 {
-	X509_NAME *issuer_name;
+	const X509_NAME *issuer_name;
 	X509 *issuer;
 	X509_STORE_CTX *storectx = NULL;
 	X509_OBJECT *obj = NULL;
