Signing with SHA256 by Smartcard?

[NIIBE Yutaka]

I am trying to use Gnuk USB Token for Debian Developers, who
requires SHA256.

Today, I found that current Gnuk only supports digital signing for
SHA-1 DigestInfo.  So, I fixed to support SHA256 DigestInfo.

But, it seems that GnuPG does not support SHA256 DigestInfo for SmartCard
well.  Yes, the function cmd_pksign in scd/command.c has support of
option like: --hash=XXX.  But, caller side function agent_card_pksign
in agent/call-scd.c doesn't use this option at all.

Don't we need to fix agent/call-scd.c?
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