If the `string` property of the item that is added is an alias to the
`string` parameter of `add_item_to_object`, and `constant` is false,
`cJSON_strdup` would access the string after it has been freed.

Thanks @hhallen for reporting this in #248.

Thanks @liuyunbin for reporting this in #230

Thanks @liuyunbin for reporting this in #230

Thanks @liuyunbin for reporting this in #230

These functions return the added object. Functions to add objects and
arrays have also been added.

A macro named `ENABLE_LOCALES` was added and an option with the same name too in the CMakeLists.txt

pointer in error case and change code to match new expectations.

If realloc returns NULL, ensure didn't abort but returned
printbuffer.offset instead. If an attacker can control
printbuffer.offset and also make realloc fail at just the right moment,
this would make cJSON potentially write at an arbitrary memory address.

This has been detected via MSVC's Warning C4668

C89 sadly doesn't provide safe alternatives for strcpy, sprintf and the
like.