API for pressure-sensitive pens + XInput2/Wayland

This patch adds an API for querying pressure-
sensitive pens, cf. SDL_pen.h:
- Enumerate all pens
- Get pen capabilities, names, GUIDs
- Distinguishes pens and erasers
- Distinguish attached and detached pens
- Pressure and tilt support
- Rotation, distance, throttle wheel support
  (throttle wheel untested)
- Pen type and meta-information reporting
  (partially tested)

Pen event reporting:
- Three new event structures: PenTip, PenMotion, and
  PenButton
- Report location with sub-pixel precision
- Include axis and button status, is-eraser flag

Internal pen tracker, intended to be independent
of platform APIs, cf. SDL_pen_c.h:
- Track known pens
- Handle pen hotplugging

Automatic test:
- testautomation_pen.c

Other features:
- XInput2 implementation, incl. hotplugging
- Wayland implementation, incl. hotplugging
- Backward compatibility: pen events default to
  emulating pens with mouse ID SDL_PEN_MOUSEID
- Can be toggled via SDL_HINT_PEN_NOT_MOUSE
- Test/demo program (testpen)
- Wacom pen feature identification by pen ID

Acknowledgements:
- Ping Cheng (Wacom) provided extensive feedback
  on Wacom pen features and detection so that
  hopefully untested Wacom devices have a
  realistic chance of working out of the box.

src/dynapi/SDL_dynapi.sym

@@ -940,6 +940,22 @@ SDL3_0.0.0 {
     SDL_GetVideoCaptureDevices;
     SDL_GetGamepadButtonLabelForType;
     SDL_GetGamepadButtonLabel;
+    SDL_GetPens;
+    SDL_GetPenStatus;
+    SDL_GetPenFromGUID;
+    SDL_GetPenGUID;
+    SDL_PenConnected;
+    SDL_GetPenName;
+    SDL_GetPenCapabilities;
+    SDL_GetPenType;
+    SDL_GetPens;
+    SDL_GetPenStatus;
+    SDL_GetPenFromGUID;
+    SDL_GetPenGUID;
+    SDL_PenConnected;
+    SDL_GetPenName;
+    SDL_GetPenCapabilities;
+    SDL_GetPenType;
     # extra symbols go here (don't modify this line)
   local: *;
 };

src/dynapi/SDL_dynapi_overrides.h

@@ -965,3 +965,19 @@
 #define SDL_GetVideoCaptureDevices SDL_GetVideoCaptureDevices_REAL
 #define SDL_GetGamepadButtonLabelForType SDL_GetGamepadButtonLabelForType_REAL
 #define SDL_GetGamepadButtonLabel SDL_GetGamepadButtonLabel_REAL
+#define SDL_GetPens SDL_GetPens_REAL
+#define SDL_GetPenStatus SDL_GetPenStatus_REAL
+#define SDL_GetPenFromGUID SDL_GetPenFromGUID_REAL
+#define SDL_GetPenGUID SDL_GetPenGUID_REAL
+#define SDL_PenConnected SDL_PenConnected_REAL
+#define SDL_GetPenName SDL_GetPenName_REAL
+#define SDL_GetPenCapabilities SDL_GetPenCapabilities_REAL
+#define SDL_GetPenType SDL_GetPenType_REAL
+#define SDL_GetPens SDL_GetPens_REAL
+#define SDL_GetPenStatus SDL_GetPenStatus_REAL
+#define SDL_GetPenFromGUID SDL_GetPenFromGUID_REAL
+#define SDL_GetPenGUID SDL_GetPenGUID_REAL
+#define SDL_PenConnected SDL_PenConnected_REAL
+#define SDL_GetPenName SDL_GetPenName_REAL
+#define SDL_GetPenCapabilities SDL_GetPenCapabilities_REAL
+#define SDL_GetPenType SDL_GetPenType_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -998,3 +998,11 @@ SDL_DYNAPI_PROC(void,SDL_CloseVideoCapture,(SDL_VideoCaptureDevice *a),(a),)
 SDL_DYNAPI_PROC(SDL_VideoCaptureDeviceID*,SDL_GetVideoCaptureDevices,(int *a),(a),return)
 SDL_DYNAPI_PROC(SDL_GamepadButtonLabel,SDL_GetGamepadButtonLabelForType,(SDL_GamepadType a, SDL_GamepadButton b),(a,b),return)
 SDL_DYNAPI_PROC(SDL_GamepadButtonLabel,SDL_GetGamepadButtonLabel,(SDL_Gamepad *a, SDL_GamepadButton b),(a,b),return)
+SDL_DYNAPI_PROC(SDL_PenID*,SDL_GetPens,(int *a),(a),return)
+SDL_DYNAPI_PROC(Uint32,SDL_GetPenStatus,(SDL_PenID a, float *b, float *c, float *d, size_t e),(a,b,c,d,e),return)
+SDL_DYNAPI_PROC(SDL_PenID,SDL_GetPenFromGUID,(SDL_GUID a),(a),return)
+SDL_DYNAPI_PROC(SDL_GUID,SDL_GetPenGUID,(SDL_PenID a),(a),return)
+SDL_DYNAPI_PROC(SDL_bool,SDL_PenConnected,(SDL_PenID a),(a),return)
+SDL_DYNAPI_PROC(const char*,SDL_GetPenName,(SDL_PenID a),(a),return)
+SDL_DYNAPI_PROC(Uint32,SDL_GetPenCapabilities,(SDL_PenID a, SDL_PenCapabilityInfo *b),(a,b),return)
+SDL_DYNAPI_PROC(SDL_PenSubtype,SDL_GetPenType,(SDL_PenID a),(a),return)

src/dynapi/gendynapi.py

@@ -379,7 +379,7 @@ def check_comment():
         if header != 'SDL_stdinc.h':
             parameter_name = i['parameter_name']
             for n in parameter_name:
-                if n != "" and "\\param " + n not in comment:
+                if n != "" and "\\param " + n not in comment and "\\param[out] " + n not in comment:
                     check_comment_header()
                     print("  In file %s: function %s() missing '\\param %s'" % (header, name, n));