[PATCH] ValueMapper: Eliminate cross-file co-recursion, NFC

[Rafael Espíndola via llvm-commits]

> you can probably use std::find for getMappingContextID. I wonder if it
> wouldn't be cleaner to have the caller do something like
>
> unsigned NormalID = Mapper.registerContext(...);
> unsigned AliasID = Mapped.registerContext(...);
>
> and pass the context to scheduleMap*.

Or just pass an ArrayRef of MappingContext to the constructor?

Cheers,
Rafael