[exim] Compiling errors with 4.80.1

Hello

I'm am trying to compile the latest version of Exim (4.80.1) and am
getting the error below on compilation.

Version 4.77 builds fine on the system (FreeBSD 6.1 - yes I know :-)
but I cannot build (with the same Makefile/eximon.conf) either 4.80
or 4.80.1. We have no fancy requirements in the Makefile; it's a fairly
basic config.

Here's the error:

=======================================================================
# make

>>> Creating links to source files...
>>> New Makefile & lookups/Makefile.predynamic installed
>>> Use "make makefile" if you need to force rebuilding of the makefile

/bin/sh ../scripts/Configure-os.h
/bin/sh ../scripts/Configure-os.c
gcc buildconfig.c
/bin/sh ../scripts/Configure-config.h "make"
`buildconfig' is up to date.
Building configuration file config.h
>>> config.h built

>>> version 4.80.1 #2

/bin/sh ../scripts/Configure-eximon
>>> eximon script built

gcc -DCOMPILE_UTILITY spool_in.c
In file included from spool_in.c:12:
exim.h:381: error: syntax error before "os_get_dns_resolver_res"
exim.h:381: warning: data definition has no type or storage class
*** Error code 1

Stop in /usr/src/exim/exim-4.80.1/build-FreeBSD-i386.
*** Error code 1

Stop in /usr/src/exim/exim-4.80.1.
#
=======================================================================

Any ideas what it's or I'm missing

Many thanks

Martyn Griffiths
Network Services Group
University of Glamorgan