kernel: atomic_*() functions rework

* No need for the atomically changed variables to be declared as
   volatile.
 * Drop support for atomically getting and setting unaligned data.
 * Introduce atomic_get_and_set[64]() which works the same as
   atomic_set[64]() used to. atomic_set[64]() does not return the
   previous value anymore.

headers/private/shared/Referenceable.h

@@ -30,7 +30,7 @@ protected:
 	virtual	void				LastReferenceReleased();
 
 protected:
-			vint32				fReferenceCount;
+			int32				fReferenceCount;
 };
 
 

headers/private/shared/WeakReferenceable.h

@@ -30,7 +30,7 @@ public:
 			void				GetUnchecked();
 
 private:
-			vint32				fUseCount;
+			int32				fUseCount;
 			BWeakReferenceable*	fObject;
 };
 

headers/private/shared/locks.h

@@ -71,7 +71,7 @@ int32		recursive_lock_get_recursion(recursive_lock *lock);
 #define		INIT_ONCE_UNINITIALIZED	-1
 #define		INIT_ONCE_INITIALIZED	-4
 
-status_t	__init_once(vint32* control, status_t (*initRoutine)(void*),
+status_t	__init_once(int32* control, status_t (*initRoutine)(void*),
 				void* data);
 
 #ifdef __cplusplus