The capsicum patch can be used on vanilla 8.1-RELEASE sources. Just
apply the patch and make sure you follow the build and install
instructions below.

cd /usr/src
fetch http://people.freebsd.org/~niels/capsicum/capsicum-8.1-RELEASE-26-09-2010.diff
patch -p1 < capsicum-8.1-RELEASE-26-09-2010.diff
make buildworld
make buildkernel KERNCONF=CAPABILITIES
make installkernel KERNCONF=CAPABILITIES
reboot
cd /usr/src
mergemaster -p
make installworld
reboot