Convert IEffect and IEffectClient to AIDL

This change replaces the manually-parceled IEffect and IEffectClient
with AIDL definitions.

In addition, this includes a small library that facilitates shared
memory regions over AIDL.

Bug: 160253486
Test: Ran effects-related CTS tests. Manual verification of basic
      audio functionality on Sargo.

Change-Id: I5a9c5f2f24c10072ad5067acc71aa30581af41c1
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 90b59b3..6302fc4 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -116,6 +116,8 @@
 
 namespace android {
 
+using media::IEffectClient;
+
 // retry counts for buffer fill timeout
 // 50 * ~20msecs = 1 second
 static const int8_t kMaxTrackRetries = 50;