The enum_trait_object attribute macro can be used to define an enum where
each variant holds an implementor of a trait. It implements all
methods to forward to the underlying object, as well as `From` impls.
This an aliternative to using trait objects that gets along nicer
with `gc-arena`.
Move the swf-rs crate into the Ruffle workspace proper instead of
having a separate repo. This makes it easier to make changes to
the SWF parsing code during development. swf-rs can still be
published as its own crate from the subfolder.
Mike Welsh