Add AES support for PIV General Authenticate

This adds algorithm IDs 0xA, 0xA, 0xC which as documented
by the NIST PIV specification is algorithms AES-128, AES-192
and AES-256 respectively.

This patch also addresses some of the hardcodes that prevented
nonces greater than the single byte TLV length tags would allow.
It was explicitly tested with AES-256 and 256 byte nonces.

Signed-off-by: William Roberts <w2.roberts@samsung.com>
Merge pull request #270 from shootingatshadow/aes-support

Add AES support for PIV General Authenticate

 adds new routine sc_right_trim in sc.c and opensc.h. It is used by  PIV card driver when using the piv-tool.