arg.h wasn't used for dist.

Makefile

@@ -34,7 +34,7 @@ clean:
 dist: clean
 	@echo creating dist tarball
 	@mkdir -p st-${VERSION}
-	@cp -R LICENSE Makefile README config.mk config.def.h st.info st.1 ${SRC} st-${VERSION}
+	@cp -R LICENSE Makefile README config.mk config.def.h st.info st.1 arg.h ${SRC} st-${VERSION}
 	@tar -cf st-${VERSION}.tar st-${VERSION}
 	@gzip st-${VERSION}.tar
 	@rm -rf st-${VERSION}