WIP: Super-powered memory scheme

OH NO!! The funmap system call will unmap the grant by default, but we haven't necessarily created a grant with fmap, we may very well just have given the pointer of a physical region!

This will fail!! Is this "abuse" of fmap bad? Do we keep the phys* functions instead? If no, how do we fix this? Do we make each kernel scheme responsible for clearing up the grants themselves?

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Depends on syscall!57 (closed)