eina_value_stringshare: safer copy, to cope copying user-generated structs.

eina_value_stringshare: safer copy, to cope copying user-generated structs.

array, list, struct and others set() now copies the values. These
values can be created by user, in this case string is just a stack
object and not a real eina_stringshare.

To cope with it, add the string instead of referencing it. Bit slower,
but nicer behavior.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/eina@67886 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33