utf8_bytes() was a hack to get a particular job done in a hopefully portable manner. We needed a way to escape XML special characters. XML characters can include non-ASCII UTF-8 characters.

It's awkward, partly because it's paranoid about the value of CHAR_BIT: UTF-8 uses 8-bit bytes, while the size of a C byte is implementation-dependent.

It also may have errors. Maintainers of a widely used, general-purpose library are more likely to find and fix those errors, compared to our small group of developers with a piece of code that sees very limited use.

This task is to explore using GLib UTF-8/Unicode functions to fill the role of utf8_bytes(). We may find other uses for them as well.

GLib Unicode manipulation functions:
https://developer-old.gnome.org/glib/unstable/glib-Unicode-Manipulation.html

(using developer-old link because there is no corresponding page on the up-to-date docs)