Added parse_null test. This does not change anything with how the parser handles \u0000 or null characters
This commit is addapted from one by Adomas Paltanavičius <adomas@leanholding.com>
git-svn-id: http://svn.metaparadigm.com/svn/json-c/trunk@63 327403b1-1117-474d-bef2-5cb71233fd97