Gives all catapults a SelectionGroupName, gives all bolt shooters a SelectionGroupName and gives all siege towers and rams a SelectionGroupName. This means that if you have catapults from different civs because you captured an enemy catapult, double clicking on a catapult will select all of them regardless of civ.
Note: This patch previously was about how ptol catapults unpacked into mace catapults. Because discussion on D1473 has become controversial regarding SelectionGroupNames, the fix for the ptol/mace catapult issue has been removed from D1473 and split off into D1474.