Massive refactoring of all code + audio skeleton.

This should make it easier to find files and (in the future) split things
up into separate libraries.
It also changes around emulator initialization to make it a little more
difficult to do things out of order and a little more sensible as to when
real init work happens.
Also adding a skeleton audio system/driver and reworking CPU register
access to be more extensible.

src/xenia/apu/audio_driver.h

@@ -0,0 +1,39 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2013 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_APU_AUDIO_DRIVER_H_
+#define XENIA_APU_AUDIO_DRIVER_H_
+
+#include <xenia/core.h>
+
+
+namespace xe {
+namespace apu {
+
+
+class AudioDriver {
+public:
+  virtual ~AudioDriver();
+
+  xe_memory_ref memory() const { return memory_; }
+
+  virtual void Initialize() = 0;
+
+protected:
+  AudioDriver(xe_memory_ref memory);
+
+  xe_memory_ref memory_;
+};
+
+
+}  // namespace apu
+}  // namespace xe
+
+
+#endif  // XENIA_APU_AUDIO_DRIVER_H_