[gegl] operations/external/png-save: Fix the description

[Debarshi Ray <debarshir src gnome org>]

commit 026bfb893da520548efcda4ebb18eb4f68e88be0
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Dec 23 18:44:10 2015 +0100

    operations/external/png-save: Fix the description
    
    Sink operations don't pass the buffer through.
    
    Other file saving operations mention the library that is used to write
    the files, and it is generally useful information. So let's add that
    too.

 operations/external/png-save.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/operations/external/png-save.c b/operations/external/png-save.c
index ac58f07..b0bacd7 100644
--- a/operations/external/png-save.c
+++ b/operations/external/png-save.c
@@ -228,7 +228,7 @@ gegl_op_class_init (GeglOpClass *klass)
   "title",       _("PNG File Saver"),
   "categories" , "output",
   "description",
-        _("PNG image saver (passes the buffer through, saves as a side-effect.)"),
+        _("PNG image saver, using libpng"),
         NULL);
 
   gegl_extension_handler_register_saver (".png", "gegl:png-save");