Clean up removal of libjansson parser

Clean up removal of libjansson parser

* src/json.c (json_has_suffix, json_has_prefix): Remove unused
functions.
(json_object_key_to_iter, json_array_get, json_loads)
(json_load_callback, json_object_iter, json_object_iter_value)
(json_string_value, json_object_size, json_object_iter_key)
(json_object_iter_next, json_real_value, json_string_length)
(json_integer_value) [WINDOWSNT]: Don't DEF_DLL_FN, don't
LOAD_DLL_FN, and don't define a macro for unused libjansson
functions.
(JSON_HAS_ERROR_CODE): Remove: not used.

(cherry picked from commit c2d21bda6182511f453f7bea2cbff2e0640625c9)