Add multiprocess/multiprocess.hh to tar package

[vkuzmin-uber]

To run a model in another process, your should use code:

#include <neuropod/multiprocess/multiprocess.hh>

...

auto neuropod = neuropod::load_neuropod_in_new_process(neuropod_path);

In my project I use neuropod package libneuropod.tar.gz that contains neuropod/include directory.

This directory doesn't contain multiprocess.hh.

Should we add it to the tar package?

[VivekPanyam]

Yes we should. Good catch.

As we talked about offline, I can put up a PR to fix it or review a fix if you want to put up a PR. Either way works for me. Just let me know.

Thanks for finding this!

[vkuzmin-uber]

I have this change locally. Will create Pull request

[VivekPanyam]

Fixed by #291