When you do
```
cargo run -- --simplify-cfg --irviz test.png test.c
```
The `kecc` first tries to visualize the IR, then apply optimizations.
This should not be intended, as right now there's no way to visualize
the IR after optimizations.
* Better script names and grammar fix.
* Bump Rust
* Enforce more lints.
* Improve few struct definitions by removing box.
* Many minor implementation improvements.