Refactor LCD mod -

- pixel coordinates are always unsigned
- use `for ... in range(...)` instead of `while ...`
Enable zinc tests
Remove dummy test
Add tests to CharIO
Add tests to LCD
Refactor LCD even further -

- fix hanging test by fixing signed/unsigned types
- get rid of C copypastaz and not needed mut vars
- more refactoring of while loops
Merge pull request #80 from errordeveloper/more_int_fixes

More int type fixes and tests for drivers

Reviewed-by: farcaller