Addressing latest comments.

src/core/json/json.c

src/core/json/json.h

src/core/json/json_reader.c

src/core/json/json_reader.h

src/core/json/json_string.c

src/core/json/json_writer.c

src/core/json/json_writer.h

src/core/security/credentials.c

src/core/security/json_token.c

test/core/security/json_token_test.c