Fixed bug 3446 - The haptic API does not allow to select the direction axes

meyraud705

Added Linux implementation, otherwise you get "Unsupported direction type" error.
Added documentation to explain why one would use SDL_HAPTIC_FIRST_AXIS.

src/haptic/linux/SDL_syshaptic.c

@@ -718,7 +718,9 @@ SDL_SYS_ToDirection(Uint16 *dest, SDL_HapticDirection * src)
             *dest = (Uint16) tmp;
         }
         break;
-
+    case SDL_HAPTIC_FIRST_AXIS:
+        *dest = 0x4000;
+        break;
     default:
         return SDL_SetError("Haptic: Unsupported direction type.");
     }