Builds a mortar directly in front of you.  If the mortar has no
supply of rounds, then press your "use" button to supply it.
More mortar rounds can be obtained from ammo boxes.  You can
only carry 5 at one time. The mortar must be completely out of
supply before it can be resupplied.  When you look at the mortar,
it will display the mortar's health and the amount of rounds in its
supply in the owners team color.  To fire a supplied mortar,
press your "use" button.