mdb_ctf_vread() should allow conversion of pointer to uintptr_t
in mdb, we typically use "uintptr_t" to mean a pointer in the target's address
space. Therefore we should allow mdb_ctf_vread() to convert a pointer to a
In the future we might consider requiring pointers to be converted to uintptr_t
(as opposed to an actual pointer), so that there isn't a possibility that we
will dereference them in mdb.