json_decode: strings cut off after first null-byte

In json-c 1.3.2 executing

``` php
var_dump(json_decode('{"foo\u0000bar":"bar\u0000baz"}', true));
```

outputs

``` php
array(1) {
  ["foo"] =>
  string(3) "bar"
}
```

while in json 1.2.1 it outputs

``` php
array(1) {
  ["foobar"]=>
  string(7) "barbaz"
}
```

thus braking stuff mentioned [here](http://stackoverflow.com/a/6800644/232947) (among other things).
