Issues with the constification patches

[Aldy Hernandez]

I've been solving conflicts left and right and ran into the same set
of problems Diego describes independently.

What's up with cbsi_last()/bsi_last(), and the rest of the functions
that have been duplicated?  We really shouldn't be changing APIs here,
and if we absolutely need more than one routine, it should be done in
some automagic way.  The code duplicity throughout is silly at best.

This is a maintenance nightmare.

 > Please consider reverting these API changes.

I agree as well.

Thanks.
Aldy