Added example for make rule 'clean-local'

git-svn-id: file:///home/quintiliani/svncopy/nmxptool/trunk@695 3cd66e75-5955-46cb-a940-c26e5fc5497d

Makefile.am

@@ -3,3 +3,7 @@
 SUBDIRS = src
 dist_doc_DATA = README
 
+# http://www.gnu.org/software/automake/manual/html_node/Extending.html#Extending
+clean-local:
+	@echo "example of clean-local"
+