Attempt to deduplicate some linked list code
s/pile_object_excise/square_excise_object/g
Switch floor_carry() to using the pile_insert*() functions
Add testsuite for obj-pile linked list functions
More use of pile_insert().
Fix a bug
Add pile_check_integrity() to ensure lists make sense
Add test that checks integrity of a list after item removal
Fix bug where prev links got messed up
Add circularity checks
Comment obj-pile, remove unused function
Merge pull request #376 from takkaria/restruct

Introduce & use linked list helper functions