Eo: Added eo_event_callback_array_* functions.

Eo: Added eo_event_callback_array_* functions.

These functions let you pass an array of callbacks instead of just one.
It's more memory efficient to use this if you just add a bulk of events
on the same object.

This commits breaks ABI, and breaks API of the EO_EV_CALLBACK_ADD/DEL
signals (the event info passed).