This change does the following:
* Remove the Atomic32Wrapper and AtomicImpl classes and provide the Atomic32
implementation directly via platform specific source files.
* Move/rename/delete all source files accordingly
* The atomic value itself is now volatile. Previously it was only the pointer to
the memory that was volatile, but not the actual value.
* No additional heap allocations are now done for the atomic value.
In a follow up cl I plan to start using Atomic32 in the RefCount class in order
to fix issues reported by Coverity.
Review URL: https://webrtc-codereview.appspot.com/490004
git-svn-id: http://webrtc.googlecode.com/svn/trunk@2065 4adac7df-926f-26a2-2b94-8c16560cd09d
e84373c38f