Fix compiler error on 32-bit platforms

Our 32-bit implementation of the big hash functions had a compiler
error.  This should (hopefully) fix them.
Delete known entry from hash table

The new `cork_hash_table_delete_entry` function lets you delete an entry
from hash table more efficiently.  You pass in a `cork_hash_table_entry`
instance, instead of a key value.  This means that we don't have to
search through the hash table for the value to delete; the entry
instance acts as a pointer to the specific entry that we want to delete.