Fix hang in OOM situations

Fixes https://github.com/behdad/harfbuzz/issues/161

src/hb-buffer-private.hh

@@ -174,7 +174,11 @@ struct hb_buffer_t {
     if (have_output)
     {
       if (unlikely (out_info != info || out_len != idx)) {
-	if (unlikely (!make_room_for (1, 1))) return;
+	if (unlikely (!make_room_for (1, 1)))
+	{
+	  idx++; // So we don't hang indefinitely...
+	  return;
+	}
 	out_info[out_len] = info[idx];
       }
       out_len++;