[pathnames.h readconf.c readconf.h scp.1 sftp.1 ssh-add.1 ssh-add.c]
[ssh-agent.c ssh-keygen.1 ssh-keygen.c ssh.1 ssh.c ssh_config.5]
replace our obsolete smartcard code with PKCS#11.
ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-11/v2-20/pkcs-11v2-20.pdf
ssh(1) and ssh-keygen(1) use dlopen(3) directly to talk to a PKCS#11
provider (shared library) while ssh-agent(1) delegates PKCS#11 to
a forked a ssh-pkcs11-helper process.
PKCS#11 is currently a compile time option.
feedback and ok djm@; inspired by patches from Alon Bar-Lev
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