Remove hardcodes from Mutual Authenticate

Support nonces that are not only 8 bytes in
Mutual Authenticate. Use the witness length
to determine the nonce size, thus existing
systems using 8 bytes will continue to use 8
bytes. However, with AES 256, the nonces could
be a single block size of 16 bytes or greater.
Fix secure messaging library name on Mac OS X

Mac OS X uses "libsmm-local.3.dylib" as library name. The default value
"libsmm-local.so.3" is correct for Linux but not for Mac OS X.

This bug prevented the "opensc-tool -a" to work correctly and return the
ATR if an IAS card is present in the reader.
Merge pull request #280 from shootingatshadow/aes-support

Remove hardcodes from Mutual Authenticate
Fix compiler warning

The same function iasecc_sm_external_authentication() was declared in
two different .h files.

In file included from ../../src/libopensc/iasecc.h:27:0,
                 from sm-card-iasecc.c:44:
../../src/libopensc/iasecc-sdo.h:324:5: warning: redundant redeclaration of `iasecc_sm_external_authentication' [-Wredundant-decls]
In file included from ../../src/libopensc/opensc.h:44:0,
                 from sm-card-iasecc.c:40:
../../src/libopensc/sm.h:352:5: note: previous declaration of `iasecc_sm_external_authentication' was here
Add a --no-prompt flag to pkcs15-tool (i.e. the equivalent of the --no-prompt flag of pkcs15-init). As to aid readers with keypads (as commonly used in the medical space).