Direct from the mouth of mycroft@gnu.ai.mit.edu:
> Look for the definition of `USER_H' in Makefile.in.  Remove it.  Then
> reconfigure GCC and it should build fine.
> 
> I suppose I could make those .h files actually work for us, but I don't
> see the point when ours work fine.

I went through getting gcc 2.6.0 to compile on NetBSD, and the only file that
caused problems was the ginclude/stddef.h. The simplest thing I found was to 
copy the NetBSD stddef.h file into that directory, and I had no problems
compiling through stage3.

Ron