Change xp::ENCODING to utf-8 - implementing xp-framework/rfc#146
This is the first step, there are still quite a bit of glitches we need to
figure out, e.g. whether it is clear that the low-level APIs like io.File
and peer.Socket work with bytes, and that io.streams.TextReader should be
used to read unicode correctly (the Properties object, for instance, does
this!). Also, other modules like databases, LDAP etc. must be audited; which
means going over all modules here: https://github.com/xp-framework/