Add a bunch of C header samples for the Bayesian classifier

This pull request is a result of the discussion in #1626. It contains a whole bunch of C header files taken from https://github.com/lutoma/xelix. As it's a kernel, the headers tend to be a bit unconventional. Also, they contain a lot of structs and typedefs which were previously very underrepresented in the samples.

I know its a lot of files, but it was the only set that managed to push the misdetections as C++ down to 3.15% (from the previous 12.8%). But I'd be glad to remove some of them if you think it's too much.