Wrap Calc functions used by Stack menu.

Preliminary function inventory:

• casual-stack.el: ("l" "Left" calc-left-justify :transient t)
• casual-stack.el: ("c" "Center" calc-center-justify :transient t)
• casual-stack.el: ("r" "Right" calc-right-justify :transient t)]
• casual-stack.el: ("." "At Point" calc-truncate-stack :transient t)
• casual-stack.el: ("p" "Previous" calc-truncate-up :transient t)
• casual-stack.el: ("n" "Next" calc-truncate-down :transient t)]
• casual-stack.el: ("R" "Refresh" calc-refresh :transient t)
• casual-stack.el: ("s" "Save Settings" calc-save-modes :transient t)])