This comment does patch succesfully on 8.1-RC2

http://www.berklix.com/~jhs/src/bsd/fixes/freebsd/src/gen/sys/amd64/conf/NOTES.REL=8.0-RELEASE.diff

*** 8.0-RELEASE/src/sys/amd64/conf/NOTES	Fri Apr 23 14:10:05 2010
--- generic/src/sys/amd64/conf/NOTES	Fri Apr 23 14:12:45 2010
***************
*** 429,434 ****
--- 429,435 ----
  #XXX these 32 bit binaries is added.
  
  # Enable 32-bit runtime support for FreeBSD/i386 binaries.
+ #		((8.0-RELEASE amd64 but not i386) requires COMPAT_FREEBSD7)
  options 	COMPAT_IA32
  
  # Enable iBCS2 runtime support for SCO and ISC binaries

-------------
From: FreeBSD-gnats-submit@@freebsd.org
Date: Fri, 23 Apr 2010 17:15:56 GMT (19:15 CEST)
To: "Julian H. Stacey" <jhs@@berklix.com>

Thank you very much for your problem report.
It has the internal identification `amd64/145991'.
The individual assigned to look at your
report is: freebsd-amd64. 

You can access the state of your problem report at any time
via this link:

http://www.freebsd.org/cgi/query-pr.cgi?pr=145991

>Category:       amd64
>Responsible:    freebsd-amd64
>Synopsis:       Add a requires line to /sys/amd64/conf/NOTES
>Arrival-Date:   Fri Apr 23 17:15:56 UTC 2010