Wrap getting a &mut from a static mut in an unsafe block

[jannic]

Fixes #537

[ia0]

Note that we'll probably still get the static-mut-refs lint right? (i.e. this only fixes the unsafe-op-in-unsafe-fn lint)

Not sure what's the best: just allow the lint or try to use &raw mut (but that might trigger other lints deref-addrof).

[jannic]

Note that we'll probably still get the static-mut-refs lint right? (i.e. this only fixes the unsafe-op-in-unsafe-fn lint)

Not sure what's the best: just allow the lint or try to use &raw mut (but that might trigger other lints deref-addrof).

That's already taken care of by #561

[ia0]

That's already taken care of by #561

Perfect! I didn't see it since it's not released yet and got the warning with a recent compiler.