The primary purpose of this commit is to rectify most problems with
`gsub` (and also `sub` with the `g` option), in particular fix #1425 ('\b'),
fix #2354 (lookahead), and fix #2532 (regex == `"^(?!cd ).*$|^cd "`).
This commit also partly resolves #2148 and resolves #1206 in that
`gsub` no longer loops infinitely; however, because the new `gsub`
depends critically on `match/2`, the behavior when regex == `""` is
sometimes non-standard.
The documentation has been updated to reflect the fact that `sub`
and `gsub` are intended to be regular in the second argument.
Also, `_nwise/1` has been tweaked to take advantage of TCO.
./jq --run-tests < tests/onig.test
has been run successfully:
...
Testing 'gsub("a";"b")' at line number 70
Testing 'gsub( "(.*)"; ""; "x")' at line number 74
...
22 of 22 tests passed (0 malformed)
