Use `core::ffi` over `std::os::raw` and `libc::c_*`

[waywardmonkeys]

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.

[waywardmonkeys]

This will need Rust 1.64 ...

[waywardmonkeys]

@jdm @mrobinson This is good for review now.