Builds a Creature's GUID.
Creature GUID consist of entry ID, low GUID and type ID
Player and Creature for example can have the same low GUID but not GUID.
guid = GetUnitGUID( lowguid, entry )
number lowguid
Low GUID of the Creature.
Valid numbers: integers from 0 to 4,294,967,295.
number entry
Entry ID of the Creature.
Valid numbers: integers from 0 to 4,294,967,295.
number guid
Valid numbers: integers from 0 to 18,446,744,073,709,551,615.