Patch from Shaun Jackman:
ls has an ugly bug. ls uses an array of pointers, the elements of
which are all in a linked list. To free the elements, instead of
freeing all the elements in the array, array[0..nelements], it frees
by iterating the linked list starting at array[0], which it assumes is
the head of the list. Unfortunately, ls also sorts the array! So,
array[0] is no longer the head, but somewhere in the middle of the
linked list. This patch fixes this bug, and also adds an
ENABLE_FEATURE_CLEAN_UP stanza.