Audio: Use std::deque instead of std::vector for the audio buffer type (StereoBuffer16).

The current code inserts and deletes elements from the beginning of the audio buffer, which is very inefficient in an std::vector.

Profiling was done using VisualStudio2017's Performance Analyzer in Super Mario 3D Land.

Before this change: AudioInterp::Linear had 14.14% of the runtime (inclusive) and most of that time was spent in std::vector's insert implementation.
After this change: AudioInterp::Linear has 0.36% of the runtime (inclusive)

src/audio_core/codec.h

@@ -5,13 +5,13 @@
 #pragma once
 
 #include <array>
-#include <vector>
+#include <deque>
 #include "common/common_types.h"
 
 namespace Codec {
 
 /// A variable length buffer of signed PCM16 stereo samples.
-using StereoBuffer16 = std::vector<std::array<s16, 2>>;
+using StereoBuffer16 = std::deque<std::array<s16, 2>>;
 
 /// See: Codec::DecodeADPCM
 struct ADPCMState {