#5 Function signatures wrong in hash doc

[Ken Arnold]

The doc for cp_hashtable (at least) says that the hash function signature is

long hash_fn(void *key);

but in the header file hashtable.h it's

typedef unsigned long (*cp_hashfunction)(void *);

In my compiler this mismatch generated a warning until I changed my function to comply with the header.

Also, this doc implies (almost says) that the signature for copy and destructor functions are the same, and does not give the actual signature for the destructor function.