add C yajl

[nst]

https://github.com/lloyd/yajl

request from Kurt R. by email

[anjohnson]

I suspect yajl would do well against these tests. I just ran the 318 test_parsing tests in my own test harness against a modified version of yajl that is included in a package I maintain. Apart from the 3 tests for rejecting trailing commas (I added the support for these myself; the original yajl code doesn't allow them) the only other sample that disagrees with the results here is n_structure_whitespace_formfeed.json which both versions of yajl parse without error.

The original yajl code also accepts a vertical tab character (\v in C) as white-space, which I see is also non-standard according to the original json.org spec at least; you don't seem to have any tests for that here at all.