Fix MSVC compiler and linker errors

- Fix struct/class forward declaration mismatches (JAIAudience, JASTrack) causing different MSVC mangled names and unresolved symbols
- Add jsystem_stubs.cpp with stubs for JASHeap, JASVoiceBank, J3DShapeTable, JAUSection, JHICommBuf, HIO/HIO2, JOR

src/dusk/globals.cpp

@@ -12,5 +12,10 @@ u32 __OSFpscrEnableBits;
 GDLObj* __GDCurrentDL;
 
 // DSP
+#include <dolphin/dsp.h>
 DSPTaskInfo* __DSP_first_task;
 DSPTaskInfo* __DSP_curr_task;
+
+// mDo_dvd
+#include <m_Do/m_Do_dvd_thread.h>
+u8 mDoDvdThd::DVDLogoMode;