Updated help information for adig, acountry, and ahost. #334
I was able to get Travis to pass with code in header but not in the '.c' (see be57554..., 6e9bae7...) not sure if this has to do with the 'Quick hack...' where it looks like ares_get_opt is manually included in some of the makefiles (e.g. Makefile.m32 at line 42) or if this is some other subtlety that I am not familiar with. In the case that I need to manually include in makefiles via the hack, this seems like more editing than should be needed for a simple help printout, thus perhaps I missed something. Currently all checks have passed.