[fix] Replacing ssize_t -> int

[zamazan4ik]

ssize_t is not standard ISO type. I think, you should use int instead of ssize_t.

[FooBarWidget]

Thank you for the pull request. But sorry, I don't think this is a good idea. int doesn't convey what I want to express. Especially because I use size_t elsewhere in the code, int might be too small.

If you're worried about compatibility then maybe it's a good idea to define our own sbmh_data_ssize_t type, which aliases to ssize_t when available, or int otherwise.