pgsql: So our reward for including <sys/atomic_op.h> seems to be a bunch

Log Message:
-----------
So our reward for including <sys/atomic_op.h> seems to be a bunch of
nattering about casting away volatile. Losers.

Modified Files:
--------------
pgsql/src/include/storage:
s_lock.h (r1.160 -> r1.161)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/s_lock.h.diff?r1=1.160&amp;r2=1.161)