configure.ac: enable gcc's -Wshadow warning

* configure.ac (WARNLIST): Add -Wshadow to the list.

git-svn-id: http://svn.fedorahosted.org/svn/corosync/trunk@2078 fd59a12c-fef9-0310-b244-a6a79926bd2f

configure.ac

@@ -262,6 +262,7 @@ EXTRA_WARNINGS=""
 
 WARNLIST="
 	all
+	shadow
 	missing-prototypes
 	missing-declarations
 	strict-prototypes