cfg: turn a handful of parameter parsing errors into fatal (#554)

For parameters that require two values (`width, height` or `x, y`), if
the string fails to parse, turn into runtime failure.

src/spice2x/overlay/windows/iidx_sub.cpp

@@ -13,7 +13,7 @@ namespace overlay::windows {
 
         if (GRAPHICS_IIDX_WSUB) {
             this->disabled_message =
-                "Close this overlay and use the second window.\n"
+                "Close this overlay and use the second window (ALT+TAB).\n"
                 "If you don't see the window, double check your DLL type and apply TDJ I/O patches as needed.";
         } else if (games::iidx::IIDX_TDJ_MONITOR_WARNING) {
             this->disabled_message = "TDJ mode subscreen overlay is not compatible with -monitor option";

src/spice2x/overlay/windows/keypad.cpp

@@ -120,7 +120,7 @@ namespace overlay::windows {
             "Lightning Model cabinets (TDJ) do not have any keypads; they use the subscreen.\n\n"
             "Fullscreen mode: bind a key in Overlay tab, and press it in game to show the subscreen, "
             "then use your mouse to click. Page Up button is the default binding.\n\n"
-            "Windowed mode: look for the second window in the taskbar.\n\n"
+            "Windowed mode: look for the second window in the taskbar (or ALT+TAB).\n\n"
             "Windowed mode with -iidxnosub: bring up the subscreen overlay (default Page Up).\n\n"
             );
 

src/spice2x/overlay/windows/sdvx_sub.cpp

@@ -18,7 +18,7 @@ namespace overlay::windows {
             if (GRAPHICS_PREVENT_SECONDARY_WINDOW) {
                 this->disabled_message = "Subscreen has been disabled by the user (-sdvxnosub).";
             } else {
-                this->disabled_message = "Overlay unavailable in windowed mode! Use the second window instead.";
+                this->disabled_message = "Overlay unavailable in windowed mode! Use the second window instead. (ALT+TAB)";
             }
         }