jb: touch debounce (#798)

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

## Description of change
Debouce option for touch input. Applies to all touch handlers (rawinput,
win8, win7) since it sits at the touch layer, and then consumed by jb
touch logic.

## Testing

src/spice2x/touch/win8.cpp

@@ -12,6 +12,7 @@
 
 #include "util/libutils.h"
 #include "util/logging.h"
+#include "util/time.h"
 #include "rawinput/touch.h"
 
 // mingw does not seem to have this either
@@ -220,6 +221,7 @@ void Win8Handler::handle_message(msg_handler_result &result, HWND hWnd, UINT msg
                         .x = point.x,
                         .y = point.y,
                         .mouse = false,
+                        .down_ms = get_performance_milliseconds(),
                     };
                     TOUCH_POINTS.push_back(tp);