Update to latest bindgen and fix everything

[nlfiedler]

The most recent bindgen release (0.42.0) causes many compiler warnings and errors with magick-rust. These are probably pretty easy to fix, so now's a good time to take care of that, before we fall too far behind to be manageable.

[nlfiedler]

Unfortunately, the docker rust image fails to build because it cannot find libclang.

[nlfiedler]

Version 0.31 is okay, all versions between that and 0.42 cause bizarre compiler errors in the docker rust image, while 0.42 has the libclang path problem.

[nlfiedler]

Filed bindgen bug: https://github.com/rust-lang-nursery/rust-bindgen/issues/1411

[nlfiedler]

Actually a bug in clang-sys crate: https://github.com/KyleMayes/clang-sys/issues/83

[nlfiedler]

Tried 0.44 and that works on macOS but fails with E0204 on Linux (docker image).

[nlfiedler]

0.47.1 also has the Copy trait problem. Will need to figure out how to fix it.

[nlfiedler]

Tried version 0.51.0: works fine on macOS and fails on the Linux docker image:

the trait `std::default::Default` is not implemented for `[u8; 44]

Will keep waiting for a version that works.

[nlfiedler]

Also tried Ubuntu 18.04 and that resulted in the same compile failure. Probably a general Linux issue that rust-bindgen has yet to deal with.

[npajkovsky]

I have fixed that issue and will submit pullreq in couple hours.

[npajkovsky]

pullreq submitted.

[nlfiedler]

Fixed in commit 92b12900ab0f90d66e455ff00e1edbe724c83f6d