The Compact C Type Format in the GNU toolchain

There will be a spec by the end of the month -- and I'll add the plans for v4 into it as well so people can tell what is planned on the format front. v3 is definitely less compact than FreeBSD's format, and v4 will get that compactness back again for all but very large projects that really need the increased type range.

If we could cooperate on future improvements, I'd be very happy! (But I fear that, as usual, code reuse is difficult because libctf is in the GNU toolchain, so it's GPL... how annoying, a planned format oracle that its principal beneficiaries will probably refuse to use :( but that, I suppose, is why the format needs documentation as well.)