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/logging.h

@@ -64,6 +64,11 @@ void xe_log_line(const char* file_path, const uint32_t line_number,
 #else
 #define XELOGSDB(fmt, ...) XE_EMPTY_MACRO
 #endif
+#if XE_OPTION(LOG_APU)
+#define XELOGAPU(fmt, ...) XELOGCORE('A', fmt, ##__VA_ARGS__)
+#else
+#define XELOGAPU(fmt, ...) XE_EMPTY_MACRO
+#endif
 #if XE_OPTION(LOG_GPU)
 #define XELOGGPU(fmt, ...) XELOGCORE('G', fmt, ##__VA_ARGS__)
 #else