[gcc r13-85] dfp.m4: Add missing license header

[Christophe Lyon <clyon@gcc.gnu.org>]

https://gcc.gnu.org/g:da6d834bc2188e36e876416f25a1aee528c3484d

commit r13-85-gda6d834bc2188e36e876416f25a1aee528c3484d
Author: Christophe Lyon <christophe.lyon@arm.com>
Date:   Fri Apr 29 14:11:11 2022 +0100

    dfp.m4: Add missing license header
    
    It seems the license header was omitted when dfp.m4 was originally
    contributed in 2010 (commit 3c39bca6bbb5, r0-102573 or svn r163815.
    
    This copies the license from libdecnumber/configure.ac since dfp.m4
    was originally extracted from that file.
    
    2022-04-29  Christophe Lyon  <christophe.lyon@arm.com>
    
            config/
            * dfp.m4: Add license header.

Diff:
---
 config/dfp.m4 | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/config/dfp.m4 b/config/dfp.m4
index a137ddebf8c..5b6a3f9d114 100644
--- a/config/dfp.m4
+++ b/config/dfp.m4
@@ -1,3 +1,21 @@
+# Copyright (C) 2010-2022 Free Software Foundation, Inc.
+
+# This file is part of GCC.
+
+# GCC is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation; either version 3, or (at your option) any
+# later version.
+
+# GCC is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+# License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
 dnl @synopsis GCC_AC_ENABLE_DECIMAL_FLOAT([target triplet])
 dnl
 dnl Enable C extension for decimal float if target supports it.