hypot() on windows

Hello,

I was writing the docs for hypot() and I've discovered it is not avaliable
on windows, because of a '#ifdef HAVE_HYPOT'.

The problem is that HAVE_HYPOT is not defined, but should be:
http://msdn.microsoft.com/library/en-us/vccore98/HTML/_crt__hypot.asp

Can someone please correct this, please?

Thanks,
Nuno