use (cffi:null-pointer) instead of 0 in call to ssl-ctx-ctrl
use (cffi:null-pointer) instead of 0 in call to ssl-ctx-ctrl

 * the change from :long to :pointer requires that we use a proper null pointer instead of 0.

Ferada/cl-plus-ssl,Ferada/cl-plus-ssl,deadtrickster/cl-plus-ssl,deadtrickster/cl-plus-ssl