Auto merge of rust-lang#9126 - Jarcho:auto_deref_sugg, r=Manishearth

`explicit_auto_deref` changes

fixes rust-lang#9123
fixes rust-lang#9109
fixes rust-lang#9143
fixes rust-lang#9101

This avoid suggesting code which hits a rustc bug. Basically `&{x}` won't use auto-deref if the target type is `Sized`.

changelog: Don't suggest using auto deref for block expressions when the target type is `Sized`
changelog: Include the borrow in the suggestion for `explicit_auto_deref`
changelog: Don't lint `explicit_auto_deref` on `dyn Trait` return
changelog: Don't lint `explicit_auto_deref` when other adjustments are required
changelog: Lint `explicit_auto_deref` in implicit return positions for closures

Author: bors