[racket] Filling char arrays inside cstructs

>> I'm also beginning to use the FFI, and starting to collect examples for use.
>>
>> Here's your example:
>>
>>     https://github.com/dyoo/ffi-tutorial/tree/master/ffi/tutorial/examples/struct-with-array

> Awesome!
>
> Thank you.


No problem.  The plan is to build this cookbook of really small
examples of the FFI, order them in progression, and write the tutorial
text around them.  The example in the repo should be compilable and
executable too: just run the pre-installer.rkt in that directory
first, and it'll build the library.