`core::ffi` is the preferred way to access these type definitions.
Begin removing uses of the versions from `libc`.
`libc::c_void` is not exactly the same as `core::ffi::c_void` but
some code has tried using them interchangeably (like in io-surface).
`libc::size_t` is `usize` on all current platforms.
Bruce Mitchener
9f33b121fb