New patches for running PostgreSQL on Windows

Hi,

I have created a new patch for compiling PostgreSQL on Windows.

It requires:
- Cygwin B20.1
- a crypt library
- the cygipc package
- added the included headers (endian.h into Cygwin's include/, tcp.h into
include/netinet and un.h into include/sys)

New features:
- it creates only postgres.exe (a hybrid between .EXE and .DLL) - it is
similar to executables on Unix created with gcc -export-dynamic
- it should be possible to run it on non-binary mounts (thanks to Craig
Setera)

Bugs:
- dynamic loading still doesn't work (but it is possible to create the
modules, e.g. plpgsql.dll)
- sometimes the backend survives only one connection from a client, it
crashes before the second connection is established. I have had not time to
investigate this yet.

The binaries are also available, but they are a bit huge (~3 MB in *.tgz)
because it is compiled with debug info.

I think it should be possible to begin incorporating the patches to the main
sources. Some of the changes are new files. And the rest is ifdef-ed (or
ifeq-ed in Makefiles), so it should not interfere with other ports, I hope
:-)

Dan