scd: New option --debug-assuan-log-cats.

* scd/scdaemon.c (oDebugAssuanLogCats): New.
(opts): Add option --debug-assuan-log-cats.
(main): Implement option.
* common/asshelp.c (set_libassuan_log_cats): New.

--

The old way of setting the logging categories with an environment
variable is awkward if sdaemon is spawned from a running gpg-agent.

scd/scdaemon.c

@@ -72,6 +72,7 @@ enum cmd_and_opt_values
   oDebugAllowCoreDump,
   oDebugCCIDDriver,
   oDebugLogTid,
+  oDebugAssuanLogCats,
   oNoGreeting,
   oNoOptions,
   oHomedir,
@@ -121,6 +122,7 @@ static ARGPARSE_OPTS opts[] = {
   ARGPARSE_s_n (oDebugCCIDDriver, "debug-ccid-driver", "@"),
   ARGPARSE_s_n (oDebugDisableTicker, "debug-disable-ticker", "@"),
   ARGPARSE_s_n (oDebugLogTid, "debug-log-tid", "@"),
+  ARGPARSE_p_u (oDebugAssuanLogCats, "debug-assuan-log-cats", "@"),
   ARGPARSE_s_n (oNoDetach, "no-detach", N_("do not detach from the console")),
   ARGPARSE_s_s (oLogFile,  "log-file", N_("|FILE|write a log to FILE")),
   ARGPARSE_s_s (oReaderPort, "reader-port",
@@ -553,6 +555,9 @@ main (int argc, char **argv )
         case oDebugLogTid:
           log_set_pid_suffix_cb (tid_log_callback);
           break;
+        case oDebugAssuanLogCats:
+          set_libassuan_log_cats (pargs.r.ret_ulong);
+          break;
 
         case oOptions:
           /* config files may not be nested (silently ignore them) */