Audio framework: support for audio pre processing

Audio effect framework is extended to suport effects on
output and input audio path.

AudioFlinger: Support for audio effects and effect chains is
moved from PlaybackThread class to ThreadBase class so that
RecordThread can manage effects.
Effects of type pre processing are allowed on record thread
only. When a pre processing is enabled, the effect interface handle is
passed down to the input stream so that the audio HAL can call the
process function. The record thread loop calls the effect chain process
function that will only manage the effect state and commands and skip the
process function.

AudioRecord: The audio session is allocated before calling getInput() into
audio policy serice so that the session is known before the input theead is
created and pre processings can be created on the correct session.

AudioPolicyService: default pre processing for a given input source are
loaded from audio_effects.conf file.
When an input is created, corresponding effects are created and enabled.

Change-Id: Id17119e0979b4dcf189b5c7957fec30dc3478790
diff --git a/include/media/AudioEffect.h b/include/media/AudioEffect.h
index dd93fd8..496b23e 100644
--- a/include/media/AudioEffect.h
+++ b/include/media/AudioEffect.h
@@ -188,7 +188,7 @@
      * sessionID:   audio session this effect is associated to. If 0, the effect will be global to
      *      the output mix. If not 0, the effect will be applied to all players
      *      (AudioTrack or MediaPLayer) within the same audio session.
-     * output:  HAL audio output stream to which this effect must be attached. Leave at 0 for
+     * io:  HAL audio output or input stream to which this effect must be attached. Leave at 0 for
      *      automatic output selection by AudioFlinger.
      */
 
@@ -198,7 +198,7 @@
                   effect_callback_t cbf = 0,
                   void* user = 0,
                   int sessionId = 0,
-                  audio_io_handle_t output = 0
+                  audio_io_handle_t io = 0
                   );
 
     /* Constructor.
@@ -210,7 +210,7 @@
                     effect_callback_t cbf = 0,
                     void* user = 0,
                     int sessionId = 0,
-                    audio_io_handle_t output = 0
+                    audio_io_handle_t io = 0
                     );
 
     /* Terminates the AudioEffect and unregisters it from AudioFlinger.
@@ -232,7 +232,7 @@
                             effect_callback_t cbf = 0,
                             void* user = 0,
                             int sessionId = 0,
-                            audio_io_handle_t output = 0
+                            audio_io_handle_t io = 0
                             );
 
     /* Result of constructing the AudioEffect. This must be checked