touch: make native touch the default for iidx/sdvx/popn (#820)

## Link to GitHub Issue or related Pull Request, if one exists
Fixes #814

## Description of change
Remove iidx/sdvx/popon `native touch` options.

Remove dead code in wintouchemu that deals with these games.

Native touch is now at feature-parity with wintouchemu. Native touch
options work better with touch screens, while rawinput-based wintouchemu
has compat issues on some touchscreens. For these subscreen games
deprecate the usage of wintouchemu and make them use native touch stack
by default.

### For future consideration
Gitadora - not sure what to do with this one. We only use wintouchemu
for the single window case. For all other configurations, the game
accepts mouse and touch input without any hooks, so perhaps nothing
needs to be done here.

Nostalgia - consider moving away from wintouchemu and adopt native touch
hook here as well.

## Testing
WIP

src/spice2x/games/popn/popn.cpp

@@ -20,12 +20,10 @@
 #include "io.h"
 #include "util/deferlog.h"
 #include "touch/native/nativetouchhook.h"
-#include "misc/wintouchemu.h"
 
 namespace games::popn {
 
     bool SHOW_PIKA_MONITOR_WARNING = false;
-    bool NATIVE_TOUCH = false;
     
 #if SPICE64 && !SPICE_XP
 
@@ -715,13 +713,7 @@ namespace games::popn {
         //       00000100 0000000B 00000001  (button 9)
         //       set third column to 0 and it will work with BIO2
         
-        if (NATIVE_TOUCH) {
-            nativetouch::hook(avs::game::DLL_INSTANCE);
-        } else if (!GRAPHICS_WINDOWED) {
-            wintouchemu::FORCE = true;
-            wintouchemu::INJECT_MOUSE_AS_WM_TOUCH = true;
-            wintouchemu::hook_title_ends("", "Main Screen", avs::game::DLL_INSTANCE);
-        }
+        nativetouch::hook(avs::game::DLL_INSTANCE);
 
         sysutils::hook_EnumDisplayDevicesA();
 

src/spice2x/games/popn/popn.h

@@ -22,7 +22,6 @@ namespace games::popn {
 #endif
 
     extern bool SHOW_PIKA_MONITOR_WARNING;
-    extern bool NATIVE_TOUCH;
 
     class POPNGame : public games::Game {
     public: