regex filters (#432): scan, splits, split, sub, gsub
Fix docs YAML (introduced in #432)
Fix tests for #432
Add `def f($arg):` syntax (fix #524)
Use `def f($a): ...;` syntax for builtins
Make regexp builtins and range/3 use #524 too
Make `nwise` private
Allow any number of jq-coded function arguments
`.foo[-1] = ...` trips assertion (fix #490)
Out of bounds negative array indices should raise
More constant folding: null, true, and false

    A step towards doing constant folding for arrays and objects.
Fold constant arrays
Constant fold objects