buildworld not using proper build environment

I'm not a make(1) expert, but something appears wrong with Makefile.inc1
and the build environment it provides for buildworld.

There has been a short thread on this with the subject:
Unable to build libedit

It turns out that buildworld is using the header files in /usr/include
and not those in /usr/obj/usr/src/tmp/usr/include when compiling. I've
looked at Makefile.inc1 and it looks like the proper environment is
made for AMD64, but perhaps not for other platforms (like i386). I'm not
sure what is wrong, but I have confirmed that buildworld is using
/usr/include/histedit.h in lieu of the new version in $WORLDTMP.

Am I wrong about all of this this or is something wrong with the
buildworld. 
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman_at_es.net			Phone: +1 510 486-8634