Mute clippy transmute warnings

* `clippy::transmute_ptr_to_ref` for QGadget
* `clippy::useless_transmute` for QObject

Author: Sh3Rm4n

qmetaobject_impl/src/qobject_impl.rs

@@ -686,7 +686,7 @@ pub fn generate(input: TokenStream, is_qobject: bool, qt_version: QtVersion) ->
     } else {
         quote! {
             #[allow(unused_variables)]
-            let mut obj = ::std::mem::transmute::<*mut ::std::os::raw::c_void, &mut #name #ty_generics>(o);
+            let mut obj = &*o;
         }
     };
 
@@ -875,7 +875,12 @@ pub fn generate(input: TokenStream, is_qobject: bool, qt_version: QtVersion) ->
             .map(|arg| {
                 let n = &arg.name;
                 let ty = &arg.typ;
-                quote! { unsafe { ::std::mem::transmute::<& #ty, *mut ::std::os::raw::c_void>(& #n) } }
+                quote! {
+                    {
+                        let mut n = #n;
+                        (&mut n as *mut #ty as *mut ::std::os::raw::c_void)
+                    }
+                }
             })
             .collect();
         let array_size = signal.args.len() + 1;