it is not required that ht->t.size >= ht->min_table_size anymore

Original code always ensure ht->t.size >= ht->min_table_size.
This can be improved: ht->min_table_size should be used for allocation,
not for the bucket size in use.

Why does the original code need to always ensure this ?

  Original code don't do special alloc/free when

    ht->t.size < ht->min_table_size

  in init_table()/fini_table(), so we have to force

    ht->t.size >= ht->min_table_size.

Why does new code become flexible ?

  New code use the wrappers, they handle the special cases.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>