Extend the libsa loadfile(9) granularity to tell apart randomness from the rest

Extend the libsa loadfile(9) granularity to tell apart randomness from the rest
of the kernel, and extend the array filled by loadfile to report the location
of the randomness area.

This doesn't introduce any change for bootblocks (save for a slightly larger
stack usage due to the larger array), for the new {LOAD,COUNT}_RANDOM bits
are included in the {LOAD,COUNT}_ALL masks everything uses or computes from.