\brief Check the definition of a Varnode for containment If the given Varnode has a defining PcodeOp this is checked for containment. If the Varnode is an input, check if \b this covers the start of the function. Return: - 0 if cover does not contain varnode definition - 1 if there if it is contained in interior - 2 if the defining points intersect - 3 if Cover's tail is the varnode definition