warning: passing argument 2 of ‘d2i_OCSP_RESPONSE’ from incompatible pointer type [-Wincompatible-pointer-types]
   resp = d2i_OCSP_RESPONSE (NULL, &p, len);

SSL_get_tlsext_status_ocsp_resp() expects it to not be const and
causes a warning on MSVC if we make it always const, but
d2i_OCSP_RESPONSE() wants it to be const because it won't modify it.

!23 (comment 441785)