Merge: Byte data type

As discussed in #1267, we need a Byte data type to manipulate low-level data as numerics instead of how it is done for now using chars.

This PR will serve as base for future updates, notably related to #1370 which will introduce a way to express Bytes in their literal form.

Pull-Request: #1403
Reviewed-by: Romain Chanoir <chanoir.romain@courrier.uqam.ca>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Jean Privat <jean@pryen.org>