The old versions were renamed to JS_DECLARE_OLD_NATIVE_FUNCTION and
JS_DEFINE_OLD_NATIVE_FUNCTION, and will be eventually removed once all
native functions were converted to the new format.
This allows the JS side to access the wasm memory, assuming it's
exported by the module.
This can be used to draw stuff on the wasm side and display them from
the js side, for example :^)
This impl is *extremely* simple, and is missing a lot of things, it's
also not particularly spec-compliant in some places, but it's definitely
a start :^)
