Re-split OPL4 PCM instruments due to hardware differences

- MultiPCM also has level direct, so it's remained in DivInstrumentMultiPCM. everything else don't support at MultiPCM is moved into DivInstrumentOPL4PCM.
- MultiPCM can't modify ADSR envelope unless reading instrument from ROM, so I decided to remove ADSR envelope macros. these are moved into OPL4 PCM instrument.
- Save/Load of MultiPCM level direct parameter is still disabled until main version update (for disallow crash).
- Also, this PR fixes OPL4 VGM output.

src/gui/guiConst.cpp

@@ -184,6 +184,7 @@ const char* insTypes[DIV_INS_MAX+1][3]={
   {"GBA MinMod",ICON_FA_VOLUME_UP,ICON_FUR_INS_GBA_MINMOD},
   {"Bifurcator",ICON_FA_LINE_CHART,ICON_FUR_INS_BIFURCATOR},
   {"SID2",ICON_FA_KEYBOARD_O,ICON_FUR_INS_SID2},
+  {"OPL4 PCM",ICON_FA_VOLUME_UP,ICON_FUR_INS_MULTIPCM},
   {NULL,ICON_FA_QUESTION,ICON_FA_QUESTION}
 };
 
@@ -1012,6 +1013,7 @@ const FurnaceGUIColorDef guiColors[GUI_COLOR_MAX]={
   D(GUI_COLOR_INSTR_GBA_MINMOD,"",ImVec4(0.5f,0.45f,0.7f,1.0f)),
   D(GUI_COLOR_INSTR_BIFURCATOR,"",ImVec4(0.8925f,0.8925f,0.8925f,1.0f)),
   D(GUI_COLOR_INSTR_SID2,"",ImVec4(0.6f,0.75f,1.0f,1.0f)),
+  D(GUI_COLOR_INSTR_OPL4_PCM,"",ImVec4(1.0f,0.8f,0.1f,1.0f)),
   D(GUI_COLOR_INSTR_UNKNOWN,"",ImVec4(0.3f,0.3f,0.3f,1.0f)),
 
   D(GUI_COLOR_CHANNEL_BG,"",ImVec4(0.4f,0.6f,0.8f,1.0f)),