eina: increase hash matching inside of Eina_Hash.

eina: increase hash matching inside of Eina_Hash.

This is the correct implementation of the idea developped in Lucas De Marchi's blog :
http://www.politreco.com/2013/09/optimizing-hash-table-with-kmod-as-testbed/

This give an interesting +15% for all Eina_Hash user whatever hash function they use. The inlined
djb2 is still the fastest one and all other give very close result. It does increase memory foot
print, but as much as the previous way of doing it.