Add floating point volume handling to AudioMixer

Use floating point volume in AudioMixer mixing when floating
point input is used with the new mixer engine.
AudioResampler is updated to take floating point volume to match.
Both legacy integer and floating point mixer engines work.

For now, integer volume is used when the new mixer engine
runs in integer input mode, for backward compatibility with
the legacy mixer.  The new mixer engine will generally run in
floating point input mode. When the legacy path is removed,
the integer volumes will be removed.

Change-Id: I79e80c292ae7c8b8bdd0aa371a1b2c3a1b618290
diff --git a/services/audioflinger/Android.mk b/services/audioflinger/Android.mk
index 0bdf5a3..697fb37 100644
--- a/services/audioflinger/Android.mk
+++ b/services/audioflinger/Android.mk
@@ -115,6 +115,9 @@
     AudioResamplerSinc.cpp.arm \
     AudioResamplerDyn.cpp.arm
 
+LOCAL_C_INCLUDES := \
+    $(call include-path-for, audio-utils)
+
 LOCAL_SHARED_LIBRARIES := \
     libcutils \
     libdl \