Multi value

[fitzgen]

Builds on top of #102

[fitzgen]

(Note: this just enables function calls with multiple return values, it doesn't attempt to handle multi-value blocks yet, which I figure can come in follow up PRs).

[fitzgen]

Added support for multi-value blocks, which was slightly more involved since it had to mess with control frames / BlockState in the validator a bit.

[yurydelendik]

It looks good. The only question have is where I can find a spec for the encoding used in the patch? There is https://webassembly.github.io/multi-value/core/binary/types.html#function-types, but it does not match the logic at the read_type_or_func_type.

[fitzgen]

See https://webassembly.github.io/multi-value/core/binary/instructions.html#binary-blocktype and the paragraph just above it:

Block types are encoded in special compressed form, by either the byte 0x40 indicating the empty type, as a single value type, or as a type index encoded as a positive signed integer.

[yurydelendik]

Looks good with the minor changes

[fitzgen]

Pushed a new commit with feedback addressed.

[yurydelendik]

Thank you for the patch.

[fitzgen]

Thanks!