Fix a couple of trivial clippy warnings

Author: sdroege

Diff for: cairo/src/svg.rs

@@ -146,10 +146,11 @@ mod test {
         *surface.finish_output_stream().unwrap().downcast().unwrap()
     }
 
+    #[track_caller]
     fn assert_len_close_enough(len_a: usize, len_b: usize) {
         // It seems cairo randomizes some element IDs which might make one svg slightly
         // larger than the other. Here we make sure the difference is within ~10%.
-        let len_diff = (len_a as isize - len_b as isize).abs() as usize;
+        let len_diff = usize::abs_diff(len_a, len_b);
         assert!(len_diff < len_b / 10);
     }
 

Diff for: glib/src/translate.rs

@@ -958,7 +958,7 @@ macro_rules! impl_to_glib_container_from_slice_fundamental {
                 }
 
                 unsafe {
-                    let res = ffi::g_malloc(mem::size_of::<$name>() * t.len()) as *mut $name;
+                    let res = ffi::g_malloc(mem::size_of_val(t)) as *mut $name;
                     ptr::copy_nonoverlapping(t.as_ptr(), res, t.len());
                     res
                 }