[Nut-upsdev] windows_port NUT branch

[Paul Fertser]

Hi,

Frederic, big thanks for your work on this, by a coincedence it's exactly what
i need at work :)

I'm compiling your branch on Debian GNU/Linux with mingw and having some minor
troubles worth mentioning and (i hope) fixing.

I configure with
CC=586-mingw32msvc-gcc ./configure --host=i586-mingw32msvc --prefix=/c/winnut/

Interestingly, there's scripts/Windows/Makefile in the repo but it gets
overwritten by the configure process.

Other minor tweaks i had to do (probably not the most correct way, but i know
just about nothing wrt windows programming):