rustdoc adds non existent type parameters to trait from different crate.

[luqmana]

Compare the docs for RandomAccessIterator in core and in std.

    fn indexable(&self) -> uint;
    fn idx(&mut self, index: uint) -> Option<A>;

vs

    fn indexable<A>(&self) -> uint;
    fn idx<A>(&mut self, index: uint) -> Option<A>;

Those <A> don't actually exist in the code and would actually be wrong if it were there since they'd be shadowing the A from the trait.

[alexcrichton]

This is highly likely to be a dupe of #15099, closing as such, but moving the comments over there.