miller: update to 5.8.0.

ChangeLog:

Features

    The new count verb is a keystroke-saver for stats1 -a count -f
    {some field name}.

    --jsonx and --ojsonx are keystroke-savers for --json --jvstack
    and --ojson --jvstack, which is to say, multi-line pretty-printed
    JSON format.

    The new -s name=value feature for mlr put and mlr filter gives
    you simpler access to environment variables in your Miller
    script, as requested in #315.

Bugfixes

    mlr format-values is no longer SEGVing on CSV/TSV input. This
    was reported on #330.

    #313 fixes a corner case when field names within command-line
    arguments have embedded newlines.

    Line/column indicators for JSON-formatting error messages are
    now correct (previously they were showing up as 0).

    end {print NF} no longer SEGVs. This was reported in #330.

    Several broken doc links were fixed up as reported on #329.


(fcambus)