Remove the process's reservation cache and don't
bother checking if a region is safe to use.  In
cases where regions need to be synthesized rather
than properly allocated, the memory reads required
to determine whether the area is used are

- insufficient, because intermediate locations
  could be in use, and

- unsafe, because on some platforms reading from
  memory can trigger events.

All this only makes a difference on platforms
where memory allocation in the target is impossible.
Behavior on platforms where it is possible should
stay the same.

<rdar://problem/14023970>