TRUE if net is not correctly constructed, FALSE if not.
FUNCTION
The function first checks if the units in the linked list of units
(the NET field FirstUnit) are correctly ordered by traversing the list
and checking if the UNIT fields UnitId and LayerId increase.
After that, the function check_order_ids is called.
NOTE
This function is used by check_all_network.
The function may be quite time-consuming for large networks, since all paths
from an input unit to an output unit and vice versa are checked by
check_order_ids.
