Change an 'or' back to an 'add' just to seem less weird. Replace a fence at the end of write_lock with a redundant load-acquire, because that's the way to get the powerpc to generate an 'isync' and match the synchronization primitives we get on powerpc now. Restore some lost comments.
Change an 'or' back to an 'add' just to seem less weird.
Replace a fence at the end of write_lock with a redundant load-acquire,
because that's the way to get the powerpc to generate an 'isync' and match
the synchronization primitives we get on powerpc now.
Restore some lost comments.

HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit