`unwrap` function documentation don't mention implicit copyability

[metajack]

The documentation for Option unwrap (and possibly others) is currently wrong. It does not always move the value, since the value may be implicitly copyable. This needs to be mentioned in the docs, or the types that have unwrap methods should be annotated to make them not implicitly copyable (see #9098).

[metajack]

nominating production ready

[catamorphism]

Just a bug

[nikomatsakis]

We should probably not use the term move in general in the docs, preferring instead something more generic.

[emberian]

Visiting for triage. Still a problem.

[steveklabnik]

We still say move: http://doc.rust-lang.org/core/option/type.Option.html#method.unwrap