NumberLiteral should work properly when the decimal separator is not a dot

[davidnemeti]

NumberLiteral should work properly when the decimal separator is not a dot, but e.g. a comma.

Currently it does not work when there is only one digit before the comma.

E.g. using this grammar:

var number = new NumberLiteral("number") { DecimalSeparator = ',' };
number.AddPrefix("0", NumberOptions.Octal);

it should work properly for the following texts:

• "1,2"
• "0,123"