normalize modelines/headers across src/*.c

src/tree.c

@@ -1,7 +1,12 @@
 /*
  * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009-2011 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ * tree.c: Everything that primarily modifies the layout tree data structure.
+ *
  */
-
 #include "all.h"
 
 struct Con *croot;