Refactor atomic integer.

Refactored atomic integer to be similar to c++11 std::atomic<int>.

Removed jdwp serial lock and reverted lock level name change from
https://googleplex-android-review.googlesource.com/#/c/327297/

Change-Id: I2229f30c4d5762a0e8c72697d6aca4683750af35
diff --git a/runtime/locks.h b/runtime/locks.h
index 91437e1..8cc39ea 100644
--- a/runtime/locks.h
+++ b/runtime/locks.h
@@ -36,7 +36,7 @@
   kUnexpectedSignalLock,
   kThreadSuspendCountLock,
   kAbortLock,
-  kJdwpSerialSocketLock,
+  kJdwpSocketLock,
   kAllocSpaceLock,
   kDefaultMutexLevel,
   kMarkSweepLargeObjectLock,