UBUNTU: [Debian] Fix 'printchanges' to work with versions containing '+'

I maintain several topic kernel branches/builds where I like to use version
strings that contain a '+' character. Today this means I can't use targets
like printchanges and insertchanges because '+' characters aren't escaped.
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

debian/rules.d/1-maintainer.mk

@@ -97,7 +97,7 @@ printenv:
 
 printchanges:
 	@baseCommit=$$(git log --pretty=format:'%H %s' | \
-		gawk '/UBUNTU: '".*Ubuntu-$(prev_fullver)"'$$/ { print $$1; exit }'); \
+		gawk '/UBUNTU: '".*Ubuntu-`echo $(prev_fullver) | sed 's/+/\\\\+/'`"'$$/ { print $$1; exit }'); \
 		git log "$$baseCommit"..HEAD | \
 		perl -w -f $(DROOT)/scripts/misc/git-ubuntu-log $(ubuntu_log_opts)