RFC: Explicit safe interfaces for unsafe code

This RFC proposes a reworking of Rust's `unsafe` features to force the programmer to declare (and think about) safety boundaries when they write unsafe code. The goal is to reduce mistakes when working with unsafe code that could ultimately affect program stability and security.

View the formatted version here:    
https://github.com/ecl3ctic/rfcs/blob/master/active/0000-explicit-safe-interfaces.md
Fixed it up, thanks.