RFR: 8194691: Cleanup unnecessary casts in Atomic/OrderAccess uses

[Kim Barrett]

Please review this removal of unnecessary casts in calls to Atomic and
OrderAccess functions.  This isn't an attempt to be complete, but
eliminates some easily found and easy to fix cases.

Also changed some uses of Atomic::add with a negated value to instead
use Atomic::sub.

I've not made any changes around JavaThreadState and
Thread::_thread_state manipulation.  That may require more refactoring
to deal with than I wanted to mix in with this otherwise fairly
straight-forward set of changes.

CR:
https://bugs.openjdk.java.net/browse/JDK-8194691

Webrev:
http://cr.openjdk.java.net/~kbarrett/8194691/open.00/

Testing:
Mach5 {hs,jdk}-tier{1,2,3}