Add Emacs mode at the top of the file

cmr=v1.7.5:ticket=4163

This commit was SVN r30381.

The following Trac tickets were found above:
  Ticket 4163 --> https://svn.open-mpi.org/trac/ompi/ticket/4163

ompi/mpi/fortran/base/attr_fn-f90-interfaces.h

@@ -1,4 +1,4 @@
-!
+! -*- f90 -*-
 ! Copyright (c) 2004-2005 The Regents of the University of California.
 !                         All rights reserved.
 ! Copyright (c) 2006-2012 Cisco Systems, Inc.  All rights reserved.