Broken links in 1.6 release notes

[vwim]

In section "Stabilized APIs" there seem to be a few broken links:

• ErrorKind::UnexpectedEof
• Vec::extend_from_slice
• Iterator::min_by_key
• Iterator::max_by_key

Maybe there are more, haven't checked them all.

[steveklabnik]

#31099 has some stuff

[steveklabnik]

All of these examples seem to be fixed now https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-160-2016-01-21