Restore the inclusion of request.cnf.c and response.cnf.c in the generated DCE/RPC MAPI dissector.

Also remove the use of proto_tree_add_text for something filterable.

Change-Id: I7c252fb24f5ab51e4d1913fe3b0e520a4150baec
Reviewed-on: https://code.wireshark.org/review/4214
Reviewed-by: Michael Mann <mmann78@netscape.net>