rc4_skip() function

rc4_skip - XOR RC4 stream to given data with skip-stream-start @key: RC4 key @keylen: RC4 key length @skip: number of bytes to skip from the beginning of the RC4 stream @data: data to be XOR'ed with RC4 stream @data_len: buf length Returns: 0 on success, -1 on failure Generate RC4 pseudo random stream for the given key, skip beginning of the stream, and XOR the end result with the data buffer to perform RC4 encryption/decryption.