CSC195, Class 41: Additional Styles of Linked Lists

Overview:
* Writing delete(list lst, void *val)
* An improved strategy: doubly-linked lists
* Detour: Design decision: Permitting different implementations
* Another improved strategy: circularly-linked lists

Notes:
* Read Gries 12 (this time for real).
* What did you think about Friday's class?  How could
  I change things to make class start on time?
* Are there questions on homework 6?
* What's wrong with addAfterCurrent?