Using the changes from @gadomski along with some additional work, to get the
generated bindings working again. Works on macOS and FreeBSD 11. A couple of
hacks are needed for FreeBSD, but nothing too serious.
Changed to use the libc prefix, and changed to use the generated enums.
Fixes#22, #15, and #14
cargo test passes
Using rust-bindgen to generate the bindings for the MagickWand library is
extremely difficult with the new versions of rust-bindgen. The old versions
of the generated bindings will be used for now, and nothing will be
generated at build time.
cargo test passes