<ws2tcpip.h> since IPv6 is no longer optional (was it ever?)

code uses that

Provided implementations of inet_net_pton and inet_pton from BIND for systems that do not include these functions. These will be necessary for CIDR support and IPv6 support.

first little steps towards IPv6 support!

sets the required HAVE_xx defines for non-DOS/Win targets.

Basically in loops like handle_errors(), 'query->next' was assigned a local
variable and then query was referenced after the memory was freed by
next_server(). I've changed that so next_server() and end_query() returns the
next query. So callers should use this ret-value.

The next problem was that 'server->tcp_buffer_pos' had a random value at entry
to 1st recv() (luckily causing Winsock to return ENOBUFS).

I've also added a ares_writev() for Windows to streamline the code
a bit more.

  check for ssize_t to make it possible to use that when receiving the send()
  error code. This is necessary to prevent compiler warnings on some systems.

- Made configure create config.h, and all source files now include setup.h that
  might include the proper config.h (or a handicrafted alternative).

- Switched to 'ares_socket_t' type for sockets in ares, since Windows don't
  use 'int' for that.

- automake-ified and libool-ified c-ares. Now it builds libcares as a shared
  lib on most platforms if wanted. (This bloated the size of the release
  archive with another 200K!)

- Makefile.am now uses Makefile.inc for the c sources, h headers and man
  pages, to make it easier for other makefiles to use the exact same set of
  files.

- Adjusted 'maketgz' to use the new automake magic when building distribution
  archives.