Add ATF update instructions and file exclude list.

Submitted by:	Garrett Cooper <yanegomi@gmail.com>

contrib/atf/FREEBSD-Xlist

@@ -0,0 +1,8 @@
+bootstrap/
+config.log
+config.status
+libtool
+Makefile
+stamp-h1
+*/*/.deps/
+*/.deps/

contrib/atf/FREEBSD-upgrade

@@ -0,0 +1,28 @@
+$FreeBSD$
+
+atf
+
+The source code is hosted on GoogleCode as a subcomponent of the Kyua project:
+
+	http://code.google.com/p/kyua/downloads/list
+
+For the contrib directory, the sources were initially prepared like so:
+
+	./configure --prefix=/ --exec-prefix=/usr --datarootdir=/usr/share
+
+For the contrib directory, files and directories were pruned by:
+
+sh -c 'for F in `cat FREEBSD-Xlist`; do rm -rf ./$F ; done'
+
+You may check if there are any new files that we don't need.
+
+The instructions for importing new release and merging to HEAD can be found
+at FreeBSD wiki:
+
+	http://wiki.freebsd.org/SubversionPrimer/VendorImports
+
+To make local changes to atf, simply patch and commit to the trunk
+branch (aka HEAD).  Never make local changes on the vendor branch.
+
+gcooper@FreeBSD.org
+5-August-2012