First Phase 4 batch: the host-coupled fns whose logic is pure composition of
existing core primitives, so no new jolt.host surface is needed. vary-meta is
just (with-meta obj (apply f (meta obj) args)); namespace-munge is a char map
over str. Both land in the 20-coll tier; the Janet core-* defns and bindings
are gone. Added namespace-munge spec cases and a vary-meta extra-args case.
The heavily host-coupled fns (atom/var/transient internals, arrays, proxy,
futures) stay in Janet pending a thin host-primitive expansion.
e6ff4b8a77