Add `module` directive, `modulemeta` builtin

    Fix #425.
Document module system

    Fix #511.
BSD sed lacks -r; fix #551
Drop "any/" in module search; use 1.x-master
Quiet warning about freopen() of stdout
C-coded builtins should not assert (fix #553)
Properly handle incomplete json when input is file

Fix #562
Handle invalid inputs in argument files (fix #562)
Never close stdin; allow multiple `-` arguments
Drop the jq version directory from search path
Properly handle when objects cannot be folded

Fix #579.
to_entries should not sort keys (fix #561)
Remove sort/1 and group/1

Reserve these for sorting with jq-coded comparators.
from-entries should work with EC2 (fix #592)
Update docs about sort/group/min/max/unique
Restore `split/1`; don't use regexp (fix #576)
WIP: Add support for JSON sequence