patch 8.0.1773: dialog messages are not translated

Problem:    Dialog messages are not translated.
Solution:   Add N_() and _() where needed. (Sergey Alyoshin)
diff --git a/src/message.c b/src/message.c
index 25c22f6..f9ae0e9 100644
--- a/src/message.c
+++ b/src/message.c
@@ -4057,7 +4057,7 @@
 	}
 	else
 	    fname = gui_mch_browse(flags & BROWSE_SAVE,
-					   title, dflt, ext, initdir, filter);
+			       title, dflt, ext, initdir, (char_u *)_(filter));
 
 	/* We hang around in the dialog for a while, the user might do some
 	 * things to our files.  The Win32 dialog allows deleting or renaming