David Vasek authored Apr 27, 2022 and Libor Peltan committed May 02, 2022

Current code as used by evsched_schedule() has led to a corrupted heap
(with its elements out of order), resulting in unpredictable event scheduling
behaviour, including events being processed out of order or already scheduled
events being postponed, sometimes for several days, weeks, or maybe longer.

Solving it by modifying the heap.c library a little -- the new code properly
handles a situation when the original element and the element it's being replaced by
are identical (that is, the same memory object), but already containing a modified
value than what originally was in the heap. Instead of comparing the new element
with the one it replaces, we now start comparing it with its parent.

This commit fixes an old bug introduced in:
925ad42d