This is useful to programmatically find out the version of cJSON that
has been used (useful in case of scripting language bindings for
example).

This is important so that it is always known which version of the
library is used, especially if the C and Header files have just been
copy pasted to another code base.

Add support for raw JSON

Fix bad CMake argument in README

Introduce compiler check if const is casted away.

There was a long running discussion here
https://github.com/DaveGamble/cJSON/pull/80 how to provide const
correctness for users of cJSON.

To avoid breaking changes for users of cJSON v1 it was decided to
disable this warning.

pragma was tested with gcc 5.4.0/6.2.1 and clang 3.8/3.9.

fix memory leak in cJSON_Duplicate

Add a comment that warns about potential write access to constant memory
locations after using cJSON_AddItemToObjectCS.

Make print_preallocated static.

Otherwise compilation failes due to missing prototypes.