message: simplify get_context_data and get_context_data_mut
diff: @@ -136,17 +136,11 @@ fn destroy_unmanaged_context_data<S: Storage, Q: Querier>(ptr: *mut c_void) {
  fn get_context_data_mut<'a, 'b, S: Storage, Q: Querier>(
  ctx: &'a mut Ctx,
  ) -> &'b mut ContextData<'b, S, Q> {
  - let owned = unsafe {
  - Box::from_raw(ctx.data as *mut ContextData<S, Q>) // obtain ownership
  - };
  - Box::leak(owned) // give up ownership
  + unsafe { &mut *(ctx.data as *mut ContextData<S, Q>) }
  }
  fn get_context_data<'a, 'b, S: Storage, Q: Querier>(ctx: &'a Ctx) -> &'b ContextData<'b, S, Q> {
  - let owned = unsafe {
  - Box::from_raw(ctx.data as *mut ContextData<S, Q>) // obtain ownership
  - };
  - Box::leak(owned) // give up ownership
  + unsafe { &*(ctx.data as *mut ContextData<S, Q>) }
  }
  /// Creates a back reference from a contact to its partent instance
  