This is what's new and changed in the c-ares 1.6.0 release:

Changed:

 o Added support for the glibc "rotate" resolv.conf option (or ARES_OPT_ROTATE)
 o Added ares_gethostbyname_file()
 o Added ares_dup()
 o Added ares_set_socket_callback()

Fixed:

 o improved configure detection of several functions
 o improved source code portability
 o adig supports a regular numerical dotted IP address for the -s option
 o handling of EINPROGRESS for UDP connects
 o ares_parse_ptr_reply()would cause a buffer to shrink instead of expand if a
   reply contained 8 or more records
 o buildconf works on OS X

Thanks go to these friendly people for their efforts and contributions:

 Yang Tse, Charles Hardin, Carlo Contavalli, Brad Spencer, Gerald Combs,
 Gregor Jasny

Have fun!