case folding & internationalized names

Also flagged by @mfb:

This deserves thorough review throughout the stack. A quick band-aid patch involves lowercasing input, but we should thoroughly follow domain case folding guidelines [here](https://tools.ietf.org/html/rfc4343) and unicode's [guide for IDNs](http://unicode.org/faq/idn.html). I'm fairly sure we don't follow that last one at all, and if we do the first one, it's by accident.

Start by reading RFC 4343 and Unicode’s IDN guide linked in the issue, then trace how names are handled throughout the stack. The issue provides no files or tests; completion would require a thorough, standards-based review and implementation of case folding for internationalized names.

Written by the indexing model from the issue text.