iidx: show error message for emulated I/O mismatch in LDJ/TDJ sub overlay (#555)

## Link to GitHub Issue, if one exists
#345 

## Description of change
When DLL is configured to use TDJ I/O but spice is in LDJ mode, show an
error in LED ticker suggesting the user to turn on `-iidxtdj`.

When DLL is configured to use LDJ I/O but spice is in TDJ mode, show an
error in TDJ overaly suggesting the user to fix the DLL.

Fix a small bug that caused a white window to be created when `-w` is
enabled even when `-iidxtdj` is not, but DLL is using TDJ I/O.

src/spice2x/games/iidx/iidx.cpp

@@ -82,6 +82,7 @@ namespace games::iidx {
     bool IIDXIO_LED_TICKER_READONLY = false;
     std::mutex IIDX_LED_TICKER_LOCK;
     bool IIDX_TDJ_MONITOR_WARNING = false;
+    iidx_aio_emulation_state CURRENT_IO_EMULATION_STATE = iidx_aio_emulation_state::unknown;
 
     // io
     static bool HAS_LIBAIO; // this is how we detect iidx27+
@@ -453,7 +454,7 @@ namespace games::iidx {
         }
 
         // windowed subscreen, enabled by default, unless turned off by user
-        if (GRAPHICS_WINDOWED && !options->at(launcher::Options::spice2x_IIDXNoSub).value_bool()) {
+        if (GRAPHICS_WINDOWED && !options->at(launcher::Options::spice2x_IIDXNoSub).value_bool() && TDJ_MODE) {
             GRAPHICS_IIDX_WSUB = true;
         }
 
@@ -934,6 +935,8 @@ namespace games::iidx {
             return;
         }
 
+        CURRENT_IO_EMULATION_STATE = state;
+
         // log_warning below could be turned into log_fatal in the future once we gain confidence
         // that this isn't triggering when it's not supposed to
         if (state == iidx_aio_emulation_state::bi2a_com2 && TDJ_MODE) {