Lint unnecessary transmutes from ref to ptr

[crumblingstatue]

We already have transmute_ptr_to_ref, but we could also lint the opposite case.

 fn type_(evt: &mut sfEvent) -> *mut sfEventType {
 -    unsafe { ::std::mem::transmute(evt) }
 +    evt as *mut _ as _
  }

 fn size(evt: &mut sfEvent) -> event::Event {
 -    let e: *mut sfSizeEvent = unsafe { ::std::mem::transmute(evt) };
 +    let e: *mut sfSizeEvent = evt as *mut _ as _;
      unsafe { event::Resized { width: (*e).width, height: (*e).height } }
  }

Ref jeremyletang/rust-sfml@d84ce75?diff=unified

Edit: The as _ trick for the second as only works on 1.10 nightly (rust-lang/rust#33657)

[oli-obk]

fixed by #1045

[llogiq]

Another one bites the dust... 😄