nost: touch piano mode (#830)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change
Touch piano mode. Allows piano keys to be played with the touch screen.
Since the touch screen is still needed for menu navigation (including
during songs) a toggle switch is added so that the user can flip between
navigation mode and piano mode.

The touch targets are pixel-perfect. Don't let the game's piano
animations fool you.

## Testing

src/spice2x/touch/native/nativetouchhook.cpp

@@ -2,6 +2,9 @@
 // mingw otherwise doesn't load touch stuff
 #define _WIN32_WINNT 0x0601
 
+#include <atomic>
+
+#include "nativetouchhook.h"
 #include "avs/game.h"
 #include "rawinput/touch.h"
 #include "inject.h"
@@ -32,6 +35,7 @@ namespace nativetouch {
 
     static decltype(GetSystemMetrics) *GetSystemMetrics_orig = nullptr;
     static decltype(GetTouchInputInfo) *GetTouchInputInfo_orig = nullptr;
+    static std::atomic<TouchInputFilter> touch_input_filter { nullptr };
     static bool native_touch_hooked = false;
     static bool native_display_initialized = false;
     static DWORD native_display_orientation = DMDO_DEFAULT;
@@ -184,6 +188,22 @@ namespace nativetouch {
                     point->dwFlags = 0;
                 }
             }
+
+            const auto filter = touch_input_filter.load(std::memory_order_acquire);
+            if (point->dwFlags != 0 && filter != nullptr) {
+                const NativeTouchEvent event {
+                    .id = point->dwID,
+                    .x = point->x / 100,
+                    .y = point->y / 100,
+                    .down = (point->dwFlags & TOUCHEVENTF_DOWN) != 0,
+                    .move = (point->dwFlags & TOUCHEVENTF_MOVE) != 0,
+                    .up = (point->dwFlags & TOUCHEVENTF_UP) != 0,
+                    .synthetic = synthetic,
+                };
+                if (filter(event)) {
+                    point->dwFlags = 0;
+                }
+            }
         }
         
         return result;
@@ -193,6 +213,10 @@ namespace nativetouch {
         return native_touch_hooked;
     }
 
+    void set_input_filter(TouchInputFilter filter) {
+        touch_input_filter.store(filter, std::memory_order_release);
+    }
+
     void refresh_contact_lifetime() {
         if (settings::REFRESH_CONTACT_LIFETIME_FROM_GAME_LOOP) {
             inject::refresh_contact_lifetime();