The basic insfrastructure is built. Now I want the misc cuntions to be
more flexible and less intrusive so I will implement a mapcar function
to do virtually any lookup I want.

void* mapcar(hash_table_t table, int (*iterator)(entry_t* entry, data_pool_t* pool), data_pool_t* pool, cacher_t* cacher);

Parameters:
table: the hash table to use.
iterator: a function that
runs over the entries in reverse entry-time order. Its parameters are
the entry an the pool_data it should populate.
pool: data to be used by the iterator.
cacher: caches data and makes sure we do not iterate the same data
again. Use an empty cacher to cache new data or NULL to not use
caching at all.

data_pool_t: unsigned size, void* data;

the filter command
A pair filters current_entry_list and pipes it on to the next pair. In the end the currnet_entry_list is piped to stdout or to the next commands until filter is called again (with no arguments resets the list).

#  is aaaaa..aaa created in 22/5/2006?
filter id aaaaaaaaaaaaaaaaaaaaaaaaa date 22/5/2006
show

#all entries from 22/4/1999
filter date 22/4/1999
show

#Most recent entry
filter date MAX
show

No arguments means clear

Special values are MAX, MIN.
TODO: vlaue ranges,lists

filter* command:
Like filter but append entries to the current entry list

the show command:
shows the current current_entry_list

the append command:
adds an entry given an entry string. Omitted fields are 0

the stat command:
shows the hash table statistics.

The rm command:
removes all entries in current_entry_list from the hash table permanentrly