MFC r196334:

MFC r196334:

* Change the scope of the ASSERT_ATOMIC_LOAD() from a generic check to
  a pointer-fetching specific operation check. Consequently, rename the
  operation ASSERT_ATOMIC_LOAD_PTR().
* Fix the implementation of ASSERT_ATOMIC_LOAD_PTR() by checking
  directly alignment on the word boundry, for all the given specific
  architectures. That's a bit too strict for some common case, but it
  assures safety.
* Add a comment explaining the scope of the macro
* Add a new stub in the lockmgr specific implementation

Tested by: marcel (initial version), marius
Reviewed by: rwatson, jhb (comment specific review)
Approved by: re (kib)