Unsound implementation in load_prefix<T> and save_prefix<T>

[shinmao]

runes/src/utils.rs

Lines 71 to 75 in fd12a0a

	match reader.read(unsafe {
	from_raw_parts_mut(transmute::<*mut T, *mut u8>(obj as *mut T), len)
	}) {
	Some(x) => x == len,
	None => false,

Hi, I consider that load_prefix and save_prefix could have unsound implementation. At line 72, users could transmute arbitrary types to byte slice. However, if the types contains padding bytes, consider it as u8 could lead to undefined behavior. Based on the safety part in doc, callers are required to make sure the data points to initialized values while the function here didn't guarantee the safety.