audiopolicy: Use C++11 atomics, factor out handle generation

Update the code to use C++11 atomics. Make sure that
unsigned ints are used as id counters (signed ints have undefined
overflow behavior). Factor out common code from AudioPatch
and AudioPort.

Test: compiles
Change-Id: Ic359e97795a6282a2937d88bead8a1de27c8db7a
diff --git a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
index b717419..f680866 100644
--- a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
+++ b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
@@ -32,7 +32,6 @@
 
 #include <AudioPolicyManagerInterface.h>
 #include <AudioPolicyEngineInstance.h>
-#include <cutils/atomic.h>
 #include <cutils/properties.h>
 #include <utils/Log.h>
 #include <media/AudioParameter.h>
@@ -3437,7 +3436,7 @@
 // ----------------------------------------------------------------------------
 uint32_t AudioPolicyManager::nextAudioPortGeneration()
 {
-    return android_atomic_inc(&mAudioPortGeneration);
+    return mAudioPortGeneration++;
 }
 
 #ifdef USE_XML_AUDIO_POLICY_CONF