Inserts a new key and value into a GenericSet.
If the key already exists in the GenericSet its current value is replaced with the new
value. If you supplied a value_destroy_func when creating the GenericSet,
the old value is freed using that function. If you supplied a key_destroy_func when creating the
GenericSet, the passed key is freed using that function.
| key |
a key to insert |
| value |
the value to associate with the key |
| hash_table |
|
true if the key did not exist yet |