ASCII graphs!

We may not have a GUI like IDA, but we still have some graphs. This is a small (200 lines of code) proof of concept, but there is more to come colors utf-8 layouts resizing animations … You can try this new feature with VV if you are using radare2 from git. And by the way, this is documented, and has some tests to avoid regressions. Feel free to take a look at the /libr/cons folder if you want to contribute.