plug-ins: fix failure to load flame saved settings from file

We were using the plug-in name with underscores, which is incorrect.
Since nobody ever complained about this, this doesn't seem to be used
very often.

We will use the const that defines the plug-in name instead.

(cherry picked from commit 193596397e)

plug-ins/flame/flame.c

@@ -436,7 +436,7 @@ file_response_callback (GtkFileChooser *chooser,
           fclose (f);
           /* i want to update the existing dialogue, but it's
              too painful */
-          gimp_set_data ("plug_in_flame", &config, sizeof (config));
+          gimp_set_data (PLUG_IN_PROC, &config, sizeof (config));
           /* gtk_widget_destroy(dialog); */
           set_flame_preview ();
           set_edit_preview ();