eo: fix missing event emission

eo: fix missing event emission

There have been cases where the logic of _event_callback_call break'ed
too early in the event submission.
Reason for that was the line ((const unsigned char *) desc -
(const unsigned char *) it->desc) producing a overflow.

This means the if statement

if (!legacy_compare &&
   ((const unsigned char *) desc - (const unsigned char *) it->desc) < 0)

was true while the pointer desc was smaller than it->desc, which means
the event subscription got aborted, even if it should not.

This turned out on two 32 bit maschines. And led to not rendering apps
anymore.

It was introduced by commit in 605fec91ee7.

@fix