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/apu.cc

@@ -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. *
+ ******************************************************************************
+ */
+
+#include <xenia/apu/apu.h>
+#include <xenia/apu/apu-private.h>
+
+
+
+using namespace xe;
+using namespace xe::apu;
+
+
+DEFINE_string(apu, "any",
+    "Audio system. Use: [any, nop]");
+
+
+#include <xenia/apu/nop/nop_apu.h>
+AudioSystem* xe::apu::CreateNop(Emulator* emulator) {
+  return xe::apu::nop::Create(emulator);
+}
+
+
+AudioSystem* xe::apu::Create(Emulator* emulator) {
+  if (FLAGS_apu.compare("nop") == 0) {
+    return CreateNop(emulator);
+  } else {
+    // Create best available.
+    AudioSystem* best = NULL;
+
+    // Fallback to nop.
+    return CreateNop(emulator);
+  }
+}