After the parser returns WeaselJson_REJECT once, subsequent calls to
WeaselJsonParser_parse (including the final len==0 EOF call) must keep
returning WeaselJson_REJECT instead of potentially reporting OK.
- Add a `rejected` flag to Parser3.
- Clear the flag in reset().
- Check the flag at the start of parse() and immediately return REJECT.
- Set the flag whenever a continuation returns REJECT.
Add a test covering the exact reproduction from issue #12.
weaselbot