there was a leak of elements on the itrator stack when the stack was
flushed still having some items on it, thus losing their pointers and
never freeing them.
@fix
So it seems we are using Eina_Hash_Iterator quite a lot more than before.
This lead to a huge amount of alloc/free of Eina_Rbtree_Iterator that
was noticable in Enlightenment callgrind trace. This patch make it vanish
from the trace :-)