This allows signed decimal operands to be formatted as such, e.g.
"LDA #$FE" becomes "LDA #-2". This can be applied to immediate
operands and to numeric data pseudo-ops.
Not all assemblers support this in all situations. The asm generators
will output unsigned decimal operands if so.
The 20020- and 20022-operand-formats tests have been updated.
Andy McFadden
4ea4204ab7