Update most utilities for latest Rust

[Arcterus]

This updates all the utilities other than tee and those that were covered by @Heather.

[Arcterus]

I'm going to allow unused_must_use, at least for the time being, so that there won't be all of the warnings due to the writeln! statements.

[nutsi]

Right now, tee and wc don't build. I thik it's the same kind of errors for both (io_error doesn't exist anymore) .
I talk about dev branch

[Arcterus]

I know. @Heather's commit was doing stuff to wc, but I'll fix it. tee looked like it's going to require somewhat large changes, so I haven't done it yet.

[Arcterus]

@Heather can you merge this one too?

[Cynede]

@Arcterus you mean merge with my fork?

[Arcterus]

No, with this (uutils/coreutils). We're supposed to have other people review our changes before merging.

[Cynede]

@Arcterus ok, let me see

[Arcterus]

Thanks. 👍