Make Multiboot::new() unsafe
Make Multiboot::new() unsafe

Users must take responsibility for ensuring that the multiboot structure
is indeed where they say it is and that the paddr_to_vaddr translation
is correct.

Signed-off-by: Dan Schatzberg <2fd18fbc94e1d251ef5884a6fa05a98ae57788ae@gmail.com>

gz/rust-multiboot