The only reason to use `abort_if_errors` is when the program is so broken that either:
1. later passes get confused and ICE
2. any diagnostics from later passes would be noise
This is never the case for lints, because the compiler has to be able to deal with `allow`-ed lints.
So it can continue to lint and compile even if there are lint errors.
* renames `tests/ui/reference.{rs,stderr}` to
`tests/ui/deref_addrof.{rs,stderr}
* Moves small part of the testfile to a separate file as the lint
triggered again on the fixed code (as intended)
* Adds `// run-rustfix` to `tests/ui/deref_addrof.rs`
