BUGFIX-66

Bug 13: Bungled Burrows-Wheeler Inverse Transform

The inverse BWT takes as input a sequence of bytes. One of these bytes is distinguished as the root.
The sorted ordering of these input bytes is summarized through an exclusive prefix sum of byte counts.
The n input bytes are linked together into a circular list represented by a slice of n integers.
The i'th occurrence of byte b in the input is linked-to from the i'th occurrence of byte b in the sorted input.
Why? If two strings have the same first byte, their sorted order is determined by the bytes that follow.
Therefore, rotating (moving the first byte to the end) both strings does not change their relative order.
Traversing the linked list yields the original byte sequence (i.e., the input to the BWT).