Stairs_BuildDownSync

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31:Stairs_BuildDownSync (tag, speed, height, reset)

tag: Tag of first sector in staircase 
speed: How quickly the first step lowers 
height: Height of each step 
reset: Tics until the stairs return to their original heights (0 if never) 

Builds a staircase in sectors marked with the Stairs_Specials. Each step moves at a different speed so that they all reach their destination heights at the same time.