Untangle eggAudio a bit (#61)

* Untangle eggAudio a bit

* eggAudioRmtSpeakerMgr with a regswap

* Fix eggAudioRmtSpeakerMgr (thanks Cuyler!)

* eggAudioUtility with two regswaps

include/egg/audio/eggAudioSystem.h

@@ -1,6 +1,40 @@
 #ifndef EGG_AUDIO_SYSTEM_H
 #define EGG_AUDIO_SYSTEM_H
 
-namespace EGG {} // namespace EGG
+#include <common.h>
+
+namespace EGG {
+
+class AudioSystem {
+public:
+    AudioSystem();
+    ~AudioSystem();
+
+    void fn_804B7270(s32 frame);
+    void fn_804B7370();
+    void fn_804B73D0(s32 frame);
+    void calc();
+
+    bool isField0x04Eq2() {
+        return field_0x04 == 2;
+    }
+
+    bool field0x08NotZero() {
+        return field_0x08 != 0;
+    }
+
+    bool field0x04NotZero() {
+        return field_0x04 != 0;
+    }
+
+    static AudioSystem *sInstanse; ///< sic
+
+private:
+    f32 field_0x00;
+    s32 field_0x04;
+    s32 field_0x08;
+};
+
+} // namespace EGG
 
 #endif