needed, and being able to define it if appropriate for further configure tests
as well as for the generated config file.

Introduced reentrant.m4 intended for our reentrant related autotools/m4 macros.

  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.