This bug affects both writing and reading encrypted redo log in
MariaDB 10.1, starting from version 10.1.3 which added support for
innodb_encrypt_log. That is, InnoDB crash recovery and Mariabackup
will sometimes fail when innodb_encrypt_log is used.

MariaDB 10.2 or Mariabackup 10.2 or later versions are not affected.

log_block_get_start_lsn(): Remove. This function would cause trouble if
a log segment that is being read is crossing a 32-bit boundary of the LSN,
because this function does not allow the most significant 32 bits of the
LSN to change.

log_blocks_crypt(), log_encrypt_before_write(), log_decrypt_after_read():
Add the parameter "lsn" for the start LSN of the block.

log_blocks_encrypt(): Remove (unused function).