Returns 2-element vector containing TOUCHPixx x/y location currently being
touched. Each of the x/y coordinates ranges from 0 to 1. The coordinate space
origin is the top-left corner of the touch panel. If the panel is not currently
being touched, (0,0) will be returned. SetTouchpixxStabilizeDuration can specify
a minimal required touch duration. See Touchpixx*Demo files for examples.