Make BitLocker OpenCL format encoding-aware

In the corresponding CPU format, we have:

static void bitlocker_set_key(char *key, int index)
{
        /* Convert key to UTF-16LE (--encoding aware) */
        enc_to_utf16(saved_key[index], PLAINTEXT_LENGTH, (UTF8*)key, strlen(key));
}

static char *get_key(int index)
{
        return (char*)utf16_to_enc(saved_key[index]);
}

but there isn't an equivalent in the OpenCL format, as far as I can see. So apparently our bitlocker-opencl is currently limited to ASCII passwords, whereas the CPU format is not.

Compare the bitlocker-opencl format with the corresponding CPU format, especially bitlocker_set_key() and get_key(). Trace how the OpenCL format receives and converts passwords, then verify that non-ASCII passwords are handled consistently with the CPU format.