std::boxed::Box documentation source link broken

[nagisa]

Clicking [src] on http://doc.rust-lang.org/std/boxed/struct.Box.html will redirect to http://doc.rust-lang.org/alloc/boxed/undefined which is 404.

[tomjakubowski]

This is a dupe of #15309