Use a localized size formatting function

A similar size formatting function was used in two places in emerge
code. Instead, create a single function in portage.localization module
that formats sizes using the current locale and a common set of rules.

I'm not really convinced about 'ceiling' all sizes but I understand
the original point about not outputting '0 KiB'. If you have better
ideas, I'd be happy to change it.

The code was simplified, and a proper number formatting function
is used (instead of string splitting). Locale grouping rules are
respected now, and ISO/IEC binary prefixes are used for unambiguity.
4 files changed