rules: check we are patched

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Author:    Ian Jackson <ijackson@chiark.greenend.org.uk>
# Date:      Sat Jun 4 22:12:36 2016 +0100
#
# On branch quilt-tip-2
# Changes to be committed:
#	modified:   debian/rules
#
