libsmack: implement internal hash table of labels

Use hash table implemented internally for dictionary of labels.

Thanks to that some operations are more efficient:
-it is possible to use better hashing function than in hsearch:
 DJB2 algorithm is used, which is much better, than hashing function
 used in hsearch.
-it is possible to calculate hash during label validation.
-it would not cause drastic complexity growth to have number of labels
 near to number of allocated buckets as it happens in hsearch.
-it would be possible to add number of labels exceeding number of
 allocated buckets.

Signed-off-by: Jan Cybulski <j.cybulski@samsung.com>
libsmack: add possibility of resizing table of labels

Signed-off-by: Jan Cybulski <j.cybulski@samsung.com>