r2poke/json test

r2poke

Q: whats "fields", whats "boffsets", the offset inside looks wrong. not 0x100003a3c :?
Q: will be good to have field offsets starting from struct map address and struct mapping absolute address

```sh
$ r2 /bin/ls
[0x100003a3c]> . ./json.pk
[0x100003a3c]> ""poke type Test = struct { byte a; byte b; }
[0x100003a3c]> ""poke var root = Test@0x100003a3c#B
[0x100003a3c]> poke print json_format(root)
{"value": {"fields": [127, 35], "boffsets": [119264, 119272], "mapping": {"mapped": 1, "strict": 1, "IOS": 0, "offset": {34359857632, "type": {"code": "Offset", "info": {"magnitude": {"code": "Integral", "info": {"size": 64, "signed_p": false}}, "unit": 1}}}}}, "type": {"code": "Struct", "info": {"name": "Test", "fields": [{"name": "a", "type": {"code": "Integral", "info": {"size": 8, "signed_p": false}}}, {"name": "b", "type": {"code": "Integral", "info": {"size": 8, "signed_p": false}}}]}}}
[0x100003a3c]> _~{}
{
  "value": {
    "fields": [
      127,
      35
    ],
    "boffsets": [
      119264,
      119272
    ],
    "mapping": {
      "mapped": 1,
      "strict": 1,
      "IOS": 0,
      "offset": {
        34359857632,
        "type": {
          "code": "Offset",
          "info": {
            "magnitude": {
              "code": "Integral",
              "info": {
                "size": 64,
                "signed_p": false
              }
            },
            "unit": 1
          }
        }
      }
    }
  },
  "type": {
    "code": "Struct",
    "info": {
      "name": "Test",
      "fields": [
        {
          "name": "a",
          "type": {
            "code": "Integral",
            "info": {
              "size": 8,
              "signed_p": false
            }
          }
        },
        {
          "name": "b",
          "type": {
            "code": "Integral",
            "info": {
              "size": 8,
              "signed_p": false
            }
          }
        }
      ]
    }
  }
}
[0x100003a3c]>
```