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/d/actor/d_a_npc_taro.cpp

@@ -20,7 +20,7 @@
 #include "f_op/f_op_camera_mng.h"
 #include <dolphin/types.h>
 
-daNpc_Maro_c::actionFunc dummy_lit_3931() {
+static daNpc_Maro_c::actionFunc dummy_lit_3931() {
     return &daNpc_Maro_c::choccai;
 }