Fix for notifications in the merge folder

[Sergio Villar Senin <svillar igalia com>]

Hi,

this patch properly makes the TnyMergeFolder keep the original value of
check_duplicates that was set to the TnyFolderChange that the merge
folder receives. Otherwise it will allways return FALSE as it's the
default preset for every new TnyFolderChange.

Br

Index: libtinymail/tny-merge-folder.c
===================================================================
--- libtinymail/tny-merge-folder.c	(revision 3616)
+++ libtinymail/tny-merge-folder.c	(working copy)
@@ -1524,6 +1524,7 @@
 	TnyIterator *iter;
 	gint total = 0, unread = 0;
 	TnyList *copy;
+	gboolean check_duplicates;
 
 	g_static_rec_mutex_lock (priv->lock);
 	copy = tny_list_copy (priv->mothers);
@@ -1542,6 +1543,8 @@
 	g_object_unref (iter);
 	g_object_unref (copy);
 
+	check_duplicates = tny_folder_change_get_check_duplicates (change);
+	tny_folder_change_set_check_duplicates (new_change, check_duplicates);
 	tny_folder_change_set_new_all_count (new_change, total);
 	tny_folder_change_set_new_unread_count (new_change, unread);