Removed leading underscore in structure names

Fixes https://github.com/libsdl-org/SDL/issues/6856
Closes https://github.com/libsdl-org/SDL/pull/6914
Closes https://github.com/libsdl-org/SDL/pull/6915
Closes https://github.com/libsdl-org/SDL/pull/6916
Closes https://github.com/libsdl-org/SDL/pull/6917
Closes https://github.com/libsdl-org/SDL/pull/6918
Closes https://github.com/libsdl-org/SDL/pull/6919

include/SDL3/SDL_haptic.h

@@ -137,8 +137,8 @@ extern "C" {
  *  \sa SDL_HapticOpenFromJoystick
  *  \sa SDL_HapticClose
  */
-struct _SDL_Haptic;
-typedef struct _SDL_Haptic SDL_Haptic;
+struct SDL_Haptic;
+typedef struct SDL_Haptic SDL_Haptic;
 
 
 /**