bindings: include keystone itself on Rust bindings (#324)

bindings/const_generator.py

bindings/rust/.gitignore

bindings/rust/Cargo.toml

bindings/rust/Makefile

bindings/rust/README.md

bindings/rust/examples/asm.rs

bindings/rust/keystone-sys/Cargo.toml

bindings/rust/keystone-sys/build.rs

bindings/rust/keystone-sys/src/keystone_const.rs

bindings/rust/keystone-sys/src/lib.rs

bindings/rust/src/enums.rs

bindings/rust/src/ffi.rs

bindings/rust/src/keystone_const.rs

bindings/rust/src/lib.rs

bindings/rust/tests/keystone.rs