warning compiling math_data.C

[Angus Leeming]

André, I have a warning when compiling math_data.C. Wouldn't it be more 
elegant/comprehensible to define a MathCursor::npos if you're saying that 
the value is now invalid?

cxx: Warning: ../../../src/mathed/math_data.C, line 411: #68-D integer 
conversion resulted in a change of sign
                        mathcursor->adjust(i, -1);
----------------------------------------------^

class MathCursor {
+       static size_type const npos = static_cast<size_type>(-1);

        /// adjust position after deletion/insertion
        void adjust(pos_type from, size_type size);
};

Angus