Parsing of control characters in JSON parser

[j-moeller]

Hello,

we found an issue in the JSON parser of the project when dealing with control characters (0x00 and 0x1f). We provide a minimum working sample here: 1. For \u001f and 0x1f the ccan JSON parser becomes self-incompatible, since \u001f gets serialized to 0x1f, but 0x1f can not be parsed by the JSON parser (which is in accordance with the JSON specs).

[dgibson]

Thanks for the report. Alas, ccan is pretty moribund now, so it's probably unlikely that anything will happen about this. CCing @joeyadams who I believe is the author of that module, fwiw.