xsltproc floating-point exception

Hello all,

I was sent to this list from netbsd-users. I hope you VAX experts
might be able to help.

I am trying to build CDE (wm/cde) from pkgsrc on VAX. The help system
in CDE uses SGML, so the SGML parser OpenSP (textproc/opensp) is
required. OpenSP depends on `xmlto` (textproc/xmlto), a wrapper script
around `xsltproc` from libxslt (textproc/libxslt).

When trying to build libxslt I get many errors during the compilation
of two files, `libexslt/math.c` and `libexslt/date.c`, both part of
the libxslt extension library, libexslt. The errors are caused by
`NAN` being undefined in `<math.h>` due to the VAX's nonstandard
floating-point.

I have tried `#define NAN 0.0`, `#define NAN (0.0 / 0.0)`, `#define
NAN 1.0`, and `#define NAN xmlXPathNAN` (from libxml2). All of these
allow libxslt to compile, but installing `xmlto` fails as it tries to
build its own man pages from SGML source. `xmlto` is just a wrapper
around `xsltproc`, so I get messages saying that `xsltproc` has had a
floating point exception.
```
Floating point exception (core dumped) "/usr/pkg/bin/xsltproc" --nonet
--xinclude --p...
```

Would you know how to get around this?

Thank you.