Adds unsafe flag to skip typechecker

[filipeom]

Attemps to introduce unsafe flag for optimized owi_sym.

This flag facilitates benchmarking on WebAssembly programs derived from C code, where prior typechecking has already occurred during compilation.

[zapashcanon]

Thanks !

Could you also add the flag to the Compile.until_check function ? (you'll have to add it to all intermediate functions)

This check should also be useless in case of generated module. It's not that expensive but it may save a little bit of time.

For some reason the Check.modul function returns a module but it's the same as the original one. I'm not sure why I didn't make it return a (unit, string) Result.t instead...

[filipeom]

Done, if you want I can also change the signature of Check.modul and Compile.until_check to be of (unit, string) Result.t 😃

[zapashcanon]

Thanks.

Actually I remember now why I did this. It was a reminder to add some kind of phantom type to make sure we always go through Check.modul (it's easy to forget...). Then we would also provide a Check.modul_fake or something to typecheck when we want to be unsafe but we know what we're doing.

I'll handle this later at some point, no need for you to do it. :)