Path::new should return Option<Path> vs. failing (if there is a null byte)

[carllerche]

Failing prevents using Path::new in an embedded scenario (not wrapped in a task).

[Ryman]

Path::new_opt exists for this?

http://static.rust-lang.org/doc/master/std/path/trait.GenericPath.html#method.new_opt

[steveklabnik]

Given that rust-lang/rfcs#474 has landed, this would need another RFC to change.