Validation: description of validating the `call_indirect`, `call_ref`, and `return_call_ref` instructions

[q82419]

For applying the GC proposal, the C.types in the validation context becomes the defined types.

As the description in struct.new x for example:

• The expansion of C.types[x] must be a structure type struct fieldtype*.

For the instructions which checking the types in C.types for function types, maybe have to modify to the similar description? Take the call_ref x for example:

• Let [t1*] -> [t2*] be the function type C.types[x].

Maybe should be modified to:

• The expansion of C.types[x] must be a function type func [t1*] -> [t2*].

Thanks.

[rossberg]

Indeed, thanks! And I found a few more inconsistencies around the typing of functions, since that changed from functype to a deftype that expands to a functype. Please see #458 for a fix.

[q82419]

Close #458.