scd: Use enums for cardtype and apptype.
* scd/app-common.h (cardtype_t): New. (apptype_t): New. (struct card_ctx_s): Change type of cardtype. (struct app_ctx_s): Change type of apptype. Adjust all users. * scd/app.c (struct app_priority_list_s): Add field apptype. (strcardtype): New. Use as needed. (strapptype): New. Use as needed.
Using strcmp is lame and we can't use a switch to let the compiler
complain about missed cases.
- Signed-off-by: Werner Koch <firstname.lastname@example.org>