Initial libc-print, !println sans allocation

First attempt at packaging libc-print. This crate implements the println! and eprintln! macros without an allocator, and thus can be used in a no_std context. It is a dependency for libnotcurses-sys, which I hope to package soon.

This is my first Rust package, and I think it might have problems. I get an error about "Nick Black" not matching "Rust Packaging Team", but it seems presumptive to assume the RPT is going to take responsibility for my package? I'll happily change it, of course, if that's desirable. I looked at a few other packages and didn't see this going on, so I'm not sure what to make of it.

I also get a warning "distribution-and-changes-mismatch unstable UNRELEASED-FIXME-AUTOGENERATED-DEBCARGO", but from what I can tell, this unwieldy string is what I'm supposed to have in this file (I cannot release the package myself, being only a lowly DM). I'm not sure how I'm supposed to resolve that :/.

So I apologize for possibly submitting incomplete work, but this does build a deb, and the deb is not empty, and seems to install the needed lib.rs, so...please let me know anything further I need do.

Thanks! This closes #973916 (sorry, I didn't realize I wasn't supposed to file an ITP for Rust packages; I won't do it next time).