Un-hide the useful old div32_16.z80

[luxocrates]

The current implementation of the 32/16 divider I'm sure is a really fine algorithm, but its use of quasi-ops (for ixh/ixl) isn't ideal for a project I'm working on. Maybe other people face that constraint too...

I noticed the file's history has an earlier algorithm that uses only legal opcodes. Would you consider un-burying this one and making it a first-class citizen within the dir? I think it's a really useful piece of reference code, and thank you for it!