As it turns out, I do now have access to a NetBSD system, and will
look at that problem when I next get time.
Thanks. When you provid a patch, I will test it. (If someone else ever
wants access to a netbsd system, it's worth noting there's one on the
GCC compile farm!)
My understanding from 30589 is that a sufficiently recent version of
mingw32 has solved the problem.
The CVS version of mingw32 has the workaround, but most people aren't
using the CVS mingw32 (most people aren't using the last released
version anyway), so there'll be a need for a fix anyway.