Add two hooks allowing MD code get a MD header to be included if needed, and to override the way HEAP_START and HEAP_LIMIT are defined.
Add two hooks allowing MD code get a MD header to be included if needed,
and to override the way HEAP_START and HEAP_LIMIT are defined.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars