auto merge of #11375 : alexcrichton/rust/issue-11372, r=pcwalton

Closes #11372
Fix windows installer version to be less verbose
Update some copyright dates
Remove the io::Decorator trait

This is just an unnecessary trait that no one's ever going to parameterize over
and it's more useful to just define the methods directly on the types
themselves. The implementors of this type almost always don't want
inner_mut_ref() but they're forced to define it as well.