c0f86f5927
Explain why zero-length slices require a non-null pointer In reference to [a thread on Discourse](https://users.rust-lang.org/t/why-does-std-slice-from-raw-parts-require-a-non-null-pointer-for-zero-length-slices/10534), explain why `from_raw_parts` requires a non-null pointer for zero-length slices. r? @steveklabnik