Add native interface for activity manager service.

Fix the un/marshalling code at
frameworks/av/media/libmediaplayerservice and move it here.

Bug: 30977067
Test: Verified that transaction works fine.

Change-Id: Ice6bd1c8ebc8116147b0ca3f65a293d013edfc4c
diff --git a/libs/binder/Android.bp b/libs/binder/Android.bp
index 175e982..62b75ba 100644
--- a/libs/binder/Android.bp
+++ b/libs/binder/Android.bp
@@ -21,6 +21,7 @@
         "BpBinder.cpp",
         "BufferedTextOutput.cpp",
         "Debug.cpp",
+        "IActivityManager.cpp",
         "IAppOpsCallback.cpp",
         "IAppOpsService.cpp",
         "IBatteryStats.cpp",