sc_base64_decode - Decode a base64 stream
#include <opensc.h>
int sc_base64_decode(const char *inbuf,
unsigned char *outbuf, size_t outlen);
This function decodes the base64 stream in inbuf, which is
NULL-terminated, to the buffer pointed to by outbuf (which is outlen
bytes long);
Returns 0 if successful, or a negative value in case of error.