[mc] Enforce some assumption about the relationship of the compared areas in compare_...

[mc] Enforce some assumption about the relationship of the compared areas in compare_areas_with_type

Compare_areas_with_type expects that either :

 * both area are in the heap;
 * both area are in the current segment R/W segment.

Otherwise, it falls back to comparing pointers.

Changes to code to fail if both areas are not in the same segment