RFC: Unsafe fields.

[reem]

Add unsafe fields. Unsafe fields are declared in the definition of a
struct by prefacing them with unsafe, and a public unsafe field is
prefixed with pub unsafe. Accessing an unsafe field is unsafe.

Rendered

[reem]

This would be useful in hypers possible raw module, so that direct access to the status, headers, and body of a partially written HTTP response can be marked properly unsafe without unnecessary verbosity.

[huonw]

cc #80

[reem]

Derp. Is there much point in discussing this?

[pnkfelix]

closing as postponed.