Add distclean and maintainer-clean

GNU defines `distclean` and `maintainer-clean` as standard Makefile
targets employed for workspace cleanup. Jool's non-autogenerated
Makefiles were sometimes missing them.

Because `distclean` wasn't always defined, dpkg-buildpackage was falling
back to `clean` during the `dh_auto_clean` preparation step. `clean`
doesn't remove several build files (including Makefiles), so
`dpkg-buildpackage` was giving up after finding the workspace
contaminated.

So... implement `distclean`. This fixes Debian#1046037.

There are other GNU targets Jool is sometimes missing, but I'm pushing
that outside of the scope of this patch.

src/mod/Makefile

@@ -13,10 +13,12 @@ install:
 	$(foreach dir, $(PROJECTS), $(MAKE) -C $(dir) modules_install;)
 	/sbin/depmod
 
+distclean maintainer-clean: clean
+
 # This target is needed to generate the upstream tarball.
 # It's not a standard Kbuild target.
 distdir:
 	mkdir -p ${distdir}
 	cp -r * ${distdir}
 
-.PHONY: $(PROJECTS) $(OTHER_TARGETS) install dist
+.PHONY: $(PROJECTS) $(OTHER_TARGETS) install dist distclean maintainer-clean

src/usr/iptables/Makefile

@@ -37,7 +37,7 @@ lib%.so: lib%.o
 	${CC} -shared -fPIC ${LDFLAGS} -o $@ $^;
 lib%.o: lib%.c
 	${CC} ${DEFAULT_CFLAGS} ${CPPFLAGS} ${CFLAGS} -D_INIT=lib$*_init -fPIC -c -o $@ $<;
-clean distclean:
+clean distclean maintainer-clean:
 	rm -f *.so
 distdir:
 	mkdir -p ${distdir}