Add 'distclean' target to makefile.
diff --git a/makefile b/makefile
index 1843444..735436c 100644
--- a/makefile
+++ b/makefile
@@ -116,3 +116,6 @@
 testclean:
 	cd testdir; rm -fr arnold-fixes beebe echo foo* \
 		glop glop1 glop2 lilly.diff tempbig tempsmall time
+
+# For the habits of GNU maintainers:
+distclean: clean