Extract function doesn't preserve unsafety

[panstromek]

Problem description

Extracting block of unsafe code from unsafe function doesn't preserve its unsafety (ie. the code is not wrapped in unsafe block and the extracted function is also not unsafe.

Steps to reproduce

Before:

unsafe fn this_is_unsafe (ptr : *const u32) -> u32 {
    <span>*ptr<span>
}

After

// this code doesn't compile anymore 
unsafe fn this_is_unsafe (ptr : *const u32) -> u32 {
    extracted(ptr)
}

fn extracted(ptr: *const u32) -> u32 {
    *ptr
}