* app-p15.c (micardo_mse): New.
(do_sign): Call it.
* iso7816.c (iso7816_manage_security_env): Allow passing DATA as
NULL to indicate an empty Lc.
* tlv.c (find_tlv): Check that a found object fits into the
buffer.
(find_tlv_unchecked): New as replacement for the old non-checking
variant.
* app.c (select_application): Keep on using the non-checking
variant.
* app-openpgp.c (get_one_do, dump_all_do): Ditto.