safety checks will report null pointers and other error conditions on
public api's and can be disabled by compile time check.
note that in order to have these checks working we need to make
EINA_ARG_NONNULL() void, otherwise GCC can remove these checks since
they're known to be false.
This commit also make two minor changes:
* list and hash accessors and iterators are created even for empty
entities. This is correct in my point of view since NULL should
indicate error. Having these in were an optimziation, but not
worth it, these are not the most common case and hitting this path
is not of much cost.
* unmarked some parameters as nonnull, mainly on list and inlist.
SVN revision: 38327
ab95d9183d