Encoding an empty array or object worked, but encoding it again
(possibly after adding some items) failed, because the visited flag
(used for detecting circular references) wasn't zeroed.
* Now that JSON_SORT_KEYS is implemented, take it into use with the
valid and valid-strip suites. This is to ensure that the tests
remain valid even if the string hash function is changed in the
future.
* Remove test_dump API test. Instead, implement the same tests more
elegantly in the encoding-flags suite.
- Never append newline to output
- By default, add spaces between array and object items for more
readable output
- Introduce the flag JSON_COMPACT to not add the aforementioned spaces
Failing to do this has the effect that the error message is not
returned when the input file cannot be opened (e.g. if it doesn't
exist).
Thanks to Martin Vopatek for reporting.
