commas in numeric output

[philshafer]

Add "hn-commas" to add commas in the output of large numeric values.

Will need a command line argument to turn it off.

Should be ignored when humanize is on.

[philshafer]

Already have "comma" flag, so perhaps we should call this "numeric" since "grouping" or "thousand_sep" is mostly meaningless. This will only be triggered if there is a setting for locale.grouping and locale.thousand_sep (which is a horrible name, given that it's not specifically thousands).

% env LC_NUMERIC=en_US.UTF-8 locale -k grouping
grouping="3"
% env LC_NUMERIC=C locale -k grouping
grouping="127"