make buildworld results in 'syntax error before "TAILQ_HEAD"'

Hi,

this is the context:
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c
/usr/src/lib/libc_r/uthread/uthread_getsockname.c -o
uthread_getsockname.o
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c
/usr/src/lib/libc_r/uthread/uthread_getsockopt.c -o uthread_getsockopt.o
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c /usr/src/lib/libc_r/uthread/uthread_info.c -o
uthread_info.o
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c /usr/src/lib/libc_r/uthread/uthread_init.c -o
uthread_init.o
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c /usr/src/lib/libc_r/uthread/uthread_ioctl.c
-o uthread_ioctl.o
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c /usr/src/lib/libc_r/uthread/uthread_jmp.c -o
uthread_jmp.o
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c /usr/src/lib/libc_r/uthread/uthread_join.c -o
uthread_join.o
cc -O -pipe -mcpu=pentiumpro -DPTHREAD_KERNEL -D_THREAD_SAFE
-I/usr/src/lib/libc_r/../libc/include -I/usr/src/lib/libc_r/uthread 
-I/usr/src/lib/libc_r/../../include -D_LOCK_DEBUG
-D_PTHREADS_INVARIANTS  -c /usr/src/lib/libc_r/uthread/uthread_kern.c -o
uthread_kern.o
In file included from
/usr/obj/usr/src/i386/usr/include/sys/signalvar.h:40,
                 from /usr/src/lib/libc_r/uthread/uthread_kern.c:44:
/usr/obj/usr/src/i386/usr/include/sys/_lock.h:39: syntax error before
"TAILQ_ENTRY"
In file included from
/usr/obj/usr/src/i386/usr/include/sys/signalvar.h:41,
                 from /usr/src/lib/libc_r/uthread/uthread_kern.c:44:
/usr/obj/usr/src/i386/usr/include/sys/_mutex.h:41: syntax error before
"TAILQ_HEAD"


This is uname -a:
FreeBSD bsd-kayak.example.net 5.1-BETA FreeBSD 5.1-BETA #1: Tue May 13
22:59:39 CEST 2003    
root_at_bsd-kayak.example.net:/usr/src/sys/i386/compile/K2  i386

It is a Dual Xeon 2.4 GHu/1 GB RAM with HTT disabled in the BIOS and no
HTT in the kernel.



I'm not subscribed to this list, but I looked through the archives of
this week and nothing like this seems to have happened to anybody else.
I've build world with sources some days ago with no problems, but I had
the mozilla-build give me a gcc SIGSEGV and I thought it might be better
to upgrade...





cheers,
Rainer