Modernize signatures of method 'domain' and 'subDiff'
* 'subDiff' is now called 'subDifferential' * It returns its result in the return value, not in its second argument * The method 'domain' also returns its result in the return value
* 'subDiff' is now called 'subDifferential' * It returns its result in the return value, not in its second argument * The method 'domain' also returns its result in the return value