We have to use void in a function declaration if we want no function
parameters. Using just empty parenthesis means the function takes an
unspecified number of parameters.
Eina Value Optional can be used to create a eina value that can be set
or be empty and can be embedded in a eina_value_struct.
Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>
NOTE: EINA_VALUE_TYPE_DISPATCH_RETURN macro is a bit weird, it does
use external variable not passed to the macro and half of the parameter
given to it are just ignored...