This is a modified (simplified) version of
[termbox](https://github.com/nsf/termbox), with Rust bindings.
Main differences are:
* All input and signal handling removed (including `SIGWINCH`). For now
resizing should be done manually by setting `buffer_size_change_request`.
* Some input handling related files and functions are removed.
* utf8-related functions are removed.
(Based on [7f7694](https://github.com/nsf/termbox/commit/7f7694061d7d3eba9a7d9b6a8313155c03545e46))
1/7/2017:
* Support for terminal focus events implemented.