compatability with wasmtime 0.19.0

[plicease]

This attempts to add comparability to 0.19.0 without breaking the Perl level API. (alternative to #76)

[plicease]

I think this is the way to go, if we detect if we are using 0.19.0, and only apply this change at runtime for that version. Unfortunately, Wasmtime doesn't have an interface for determining the version

bytecodealliance/wasmtime#986

so we will have to do it by probing for unrelated symbols that only exist in 0.19.0, which is a little icky.

Down the line, we can break the Perl level API if it makes sense to do so, but we should wait until 0.19.0 has time to percolate through cpantesters etc.