HiliteItem(hMenu as Object,menuRect as Object,hitPt as Object,
previousItem as Integer, newItem as Integer)

(Maps to the kMenuHiliteItemMsg message in the Actual MDEF on Carbon and
half of the kMenuChooseMsg message under MacOS classic)

Supported platforms:
* MacOS PPC
* MacOS Carbon
* MacOS 68k
Unsupported platforms:
* Windows x86