"sys/mount.h: present but cannot be compiled"

[Gareth McCaughan]

I'm running FreeBSD 4.8, and I'm building the bundle of programs
known as "dvdrtools", which can be downloaded from
http://savannah.nongnu.org/download/dvdrtools/ .

Running the configure script gave (amid a great deal of
business-as-usual) the following:

    checking sys/mount.h usability... no
    checking sys/mount.h presence... yes
    configure: WARNING: sys/mount.h: present but cannot be compiled
    configure: WARNING: sys/mount.h: check for missing prerequisite 
headers?
    configure: WARNING: sys/mount.h: proceeding with the 
preprocessor's result
    configure: WARNING:     ## ------------------------------------ ##
    configure: WARNING:     ## Report this to address@hidden ##
    configure: WARNING:     ## ------------------------------------ ##
    checking for sys/mount.h... yes

(I apologize if my mail client has gratuitously wrapped lines;
anything there that doesn't begin with 4 spaces needs to be
joined to the line before.)

So I'm reporting it to address@hidden, as requested;
and to the dvdrtools dev list, in case the problem lies there.
I am of course aware that I may have broken my system
somehow :-).

The configure script says it was generated by GNU Autoconf
version 2.57.

The programs appear to build happily despite the warning message
(well, that's not really true, but the ways in which they fail tto
build happily have nothing to do with sys/mount.h, so far as
I can see).

-- 
Gareth McCaughan