Nightly rust complains about `cfg(..)` tests against undeclared
features and other unknown cfgs. They need to be explicitly declared
now.
The nightly/stable features don't exist, so I removed them and
substitutes the currently correct number for the single test where they
were used.
The `xmpprs_doc_build` cfg flag is now declared as expectable.
This moves InnerJid into Jid and reformulates BareJid and FullJid in
terms of Jid.
Doing this has the key advantage that FullJid and BareJid can deref to
and borrow as Jid. This, in turn, has the advantage that they can be
used much more flexibly in HashMaps. However, this is (as we say in
Germany) future music; this commit only does the internal reworking.
Oh and also, it saves 20% memory on Jid objects.
Fixes#122 more thoroughly, or rather the original intent behind it.
Since Rust 1.76, and some much older nightly, there have been
improvements to the niche computation, which leads to smaller types
which can encode the same amount of data, variants, and such.
This fixes the tests on this compiler version.
