Update FFI to latest termbox API
Update FFI to latest termbox API
Merge branch 'update' of github:mystal/rust-termbox into update

Conflicts:
	src/lib.rs
Move C FFI to termbox_sys crate
Fix name and struct repr warnings
Add constants and enums in termbox_sys

Still need to add the key constants and enums.
Use constants and enums in Rust wrapper
Rearrange items in lib

Enums first, then pub functions, and private helper functions last.
Clean up existing comments
Add Cell and Attribute enums
Expose set_cell and convenience print methods
Make Attribute and Cell fields public
impl Copy everywhere
Update rust