The host automa is used for two tasks:
* protocol sub-classification (obviously);
* DGA evaluation: the idea is that if a domain is present in this
automa, it can't be a DGA, regardless of its format/name.
In most dissectors both checks are executed, i.e. the code is something
like:
```
ndpi_match_host_subprotocol(..., flow->host_server_name, ...);
ndpi_check_dga_name(..., flow->host_server_name,...);
```
In that common case, we can perform only one automa lookup: if we check the
sub-classification before the DGA, we can avoid the second lookup in
the DGA function itself.
* Implement dga evaluation helper.
* Add test set for DGA classification.
* Add DGA classification performances tracking as part of Travis.
* Add DGA evaluation doc.
* Fix CI on OSX.
* Add missing backquote.