eina: fix Eina_Inarray API to at least match Eina_Array API.

eina: fix Eina_Inarray API to at least match Eina_Array API.

NOTE: some of this function should be moved as inline, but that's to late for a change
I think. So we will fix that if needed.

Second point, I am not happy with is eina_inarray_insert and eina_inarray_insert_at. The
naming is really poor.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/eina@70352 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33