Added 4 auxiliary buttons to the game controller API

Xbox Elite controllers use AUX1-AUX4 to represent the paddle buttons when using the HIDAPI driver
PS4 and PS5 controllers use AUX1 to represent the touchpad button
Nintendo Switch Pro controllers use AUX1 to represent the capture button

test/testgamecontroller.c

@@ -49,6 +49,10 @@ static const struct { int x; int y; } button_positions[] = {
     {154, 249},  /* DPAD_DOWN */
     {116, 217},  /* DPAD_LEFT */
     {186, 217},  /* DPAD_RIGHT */
+    {158, 0},    /* AUX1 */
+    {208, 0},    /* AUX2 */
+    {258, 0},    /* AUX3 */
+    {308, 0},    /* AUX4 */
 };
 
 /* This is indexed by SDL_GameControllerAxis. */