panic safety issue in `impl TransformContent<S, D> for [S; (2|3|4)]`

Affected versions of this crate did not guard against double drop while temporarily duplicating objects’ ownership using ptr::read(). Upon panic in a user-provided function conversion, objects that are copied by ptr::read() are dropped twice, leading to memory corruption.

The flaw was corrected in v0.9.2 by using ManuallyDrop<T> to enclose objects that are to be temporarily duplicated.