Bugzilla bug #30902: added an alternative implementation of PR_AtomicSet using cmpxchg in the comments.  Made PR_AtomicAdd a little more efficient.
Bugzilla bug #30902: added an alternative implementation of PR_AtomicSet
using cmpxchg in the comments.  Made PR_AtomicAdd a little more efficient.

makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub