add eina_inarray.

add eina_inarray.

It is an inline array, that is, the members are actually in the
allocated buffer, as opposed to a pointer to its data.

It can be used to manage array of integers, floats or other structures
without fragmenting memory.

The lookups should be fast as memory is linear, then CPU prefetch can
kick in and bring data to cache before it's used.

git-svn-id: http://svn.enlightenment.org/svn/e/trunk/eina@67003 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33