Compare the contents of this CXlConstCell with another cell
int Compare( const CXlOperBase& xlo ) const;
A reference to another CXlCell, CXlConstCell or CXlOper.
Returns 1 if the value in this object is greater than that in xlo, -1 if xlo is less and 0 if the two are equal.
This function acts like strcmp() and similar 'C' library functions.
Note that CXlOpers are sorted by type first and then value. Thus a string containing "123" will not necessarily sort later than an integer containing 122. For CXlOpers of the same type, sort order is always by value.