normalize file headers across **/*.{h,c}

include/con.h

@@ -1,3 +1,14 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009-2011 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ * con.c: Functions which deal with containers directly (creating containers,
+ *        searching containers, getting specific properties from containers,
+ *        …).
+ *
+ */
 #ifndef _CON_H
 #define _CON_H