Enum types in variadic functions aren't guaranteed to work. This is because enums for variadics undergo default argument promotion (promotion to int), and thus the user of va_arg should always get the argument as an int. Thus enums in varargs function would break on any compiler whose underlying representation is not an int (e.g., when using gcc's -fshort-enums flag)

https://stackoverflow.com/questions/73278375/do-enum-types-undergo-default-argument-promotion
https://stackoverflow.com/questions/24580503/error-when-pass-enum-in-a-function-with-variable-arguments/24580800#24580800

This pattern is used in the get_func_type function emitted as part of wasm2c modules. This PR changes this API to always use int for the var args.