[Bug c/81417] -Wsign-compare should print types being compared

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81417

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
There is more to fix, e.g. diagnostic with ?:, so not marking as resolved just
yet.