Merge: Augmented literal strings

As a follow-up to #1991, here's the support mentioned in #1734 for bytestrings, regex and raw strings

NOTE: Depends on #1991 for integration, you may review the last 3 commits while #1991 is reviewed and eventually merged

TODO: Support degraded mode (Bytes and Byte only) for byte SuperStrings instead of refusing at compile-time

Pull-Request: #1992
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --cc src/compiler/abstract_compiler.nit
Simple merge

diff --cc src/interpreter/naive_interpreter.nit
Simple merge