> it's a user-space header; I don't think it belongs in <sys/...>
> 
> maybe <__null.h>??

Before this goes much further, could something be done to make this header
available to i386 biosboot, which fails to build (-D 19991223-UTC) now that
/usr/src/sys/sys/param.h includes null.h ?

dependall ===> sys/arch/i386/stand/biosboot
...
mkdep -a -I/usr/src/sys/arch/i386/stand/biosboot/../../../..//lib/libkern/arch/i386 -DCOMPAT_OLDBOOT -DCOMPAT_386BSD_MBRPART -DSUPPORT_USTARFS -DPASS_BIOSGEOM -nostdinc -I/usr/src/sys/arch/i386/stand/biosboot -I/usr/src/sys/arch/i386/stand/biosboot/../../../../ -I/usr/src/sys/arch/i386/stand/biosboot/../../../..//arch/i386/stand/lib -I/usr/src/sys/arch/i386/stand/biosboot/../../../..//lib/libsa -D_STANDALONE   [ lots of source files, deleted ]
In file included from /usr/src/sys/arch/i386/stand/biosboot/../../../..//lib/libkern/md5c.c:33:
/usr/src/sys/arch/i386/stand/biosboot/../../../../sys/param.h:89: null.h: No such file or directory
In file included from /usr/src/sys/arch/i386/stand/biosboot/../../../..//lib/libkern/sha1.c:20:
/usr/src/sys/arch/i386/stand/biosboot/../../../../sys/param.h:89: null.h: No such file or directory
In file included from /usr/src/sys/arch/i386/stand/biosboot/../../../..//lib/libkern/pmatch.c:36:
/usr/src/sys/arch/i386/stand/biosboot/../../../../sys/param.h:89: null.h: No such file or directory
mkdep: compile failed.

Todd Whitesel
toddpw @ best.com