Fix: Adding a pilot as killboard owner by external ID

Fix for adding a pilot as new killboard owner by external ID. If an
integer is entered, the killboard tries to determine whether it was given
an internal or an external pilot ID. External pilot IDs used to be above
100.000.000 before the change to 64bit IDs. Since that, external ID have
been between 90.000.000 and 98.000.000.
Thix fix changes the lower threshold for external IDs from 100.000.000 to
90.000.000.