acountry/adig/ahost man pages

I have put together a set of man pages for the c-ares utility programs,
based on a cursory view of the programs' source files.

Feel free to edit/correct them.

Also, someone please update the usage() message in adig.c
          fprintf(stderr, "usage: adig [-f flag] [-s server] [-c class] "
          "[-t type] [-p port] name ...\n");
to something like
          fprintf(stderr, "usage: adig [-d] [-f flag] [-s server] [-c class] "
          "[-t type] [-T port] [-U port] name ...\n");
as there is no longer a -p option:
         ares_getopt(argc, argv, "df:s:c:t:T:U:")