sophie on freebsd 5 about sys/sched.h

Hi,

I use FreeBSD 5.2-Release
When I do configure to the software(Sophie-3.04rc2), I had the message:
configure: WARNING: sys/sched.h: present but cannot be compiled
configure: WARNING: sys/sched.h: check for missing prerequisite headers?
configure: WARNING: sys/sched.h: proceeding with the preprocessor's result
configure: WARNING: ## ------------------------------------ ##
configure: WARNING: ## Report this to [email protected] ##
configure: WARNING: ## ------------------------------------ ##

When I do make, I had the message:
gcc -g -O2 -Wall -Isav_if -c sophie.c
In file included from sophie.h:27,
from sophie.c:29:
/usr/include/sys/sched.h: In function `sched_pin':
/usr/include/sys/sched.h:113: error: `curthread' undeclared (first use
in this function)
/usr/include/sys/sched.h:113: error: (Each undeclared identifier is
reported only once
/usr/include/sys/sched.h:113: error: for each function it appears in.)
/usr/include/sys/sched.h: In function `sched_unpin':
/usr/include/sys/sched.h:119: error: `curthread' undeclared (first use
in this function)
*** Error code 1

What seems to be the problem ? There are similar case 
http://lists.gnu.org/archive/html/bug-autoconf/2004-05/msg00014.html

Thx & Rgds,
Frank
20040612