[gegl] operations: add some missing credits

[Téo Mazars <teom src gnome org>]

commit 46f5f16f692a171a67f2e3dc6c57f1e851488bba
Author: Téo Mazars <teomazars gmail com>
Date:   Fri Nov 15 19:14:05 2013 +0100

    operations: add some missing credits

 operations/common/stretch-contrast.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/operations/common/stretch-contrast.c b/operations/common/stretch-contrast.c
index 179cc96..de6bc2f 100644
--- a/operations/common/stretch-contrast.c
+++ b/operations/common/stretch-contrast.c
@@ -13,6 +13,7 @@
  * You should have received a copy of the GNU Lesser General Public
  * License along with GEGL; if not, see <http://www.gnu.org/licenses/>.
  *
+ * Copyright 1996 Federico Mena Quintero <federico nuclecu unam mx>
  * Copyright 2006 Øyvind Kolås <pippin gimp org>
  */