This is mostly a note to myself* before I forget: libnettle builds fine with rntcl if configured with --disable-assembler --build=x86-windows.
This is how the offcial windows builds of Pike from me are configured. Obviously this makes for a slow libnettle, but there is no extra work required to get it to work with VC6.
* And possibly to grubba. It would be nice if Roxens Xenofarm machines got a libnettle.