This is to fix the problem where `break` is dynamic, not lexical.
With this it should be possible to do this sort of thing:
label $break | inputs | if ... then $break|error else . end
This is a backwards-incompatible change for master, but the previous
`break` hadn't shipped yet.
Still needed:
- testing
Close #446.
Currently tested by disassembling and tracing various recursive jq
programs by hand under valgrind. An improved test framework that
can test for errors and specific bytecode patterns is in
development.
