List function erase is dangerous

[Iyer Arvind Sundaram]

List function erase removes the iterator passed to it. This means any operation of erase in a iterator loop, will immediately cause an error because 'i' would be freed and one would perform 'i++', where i is the iterator. A better solution would be to return the next iterator, so that one can do i=list.erase(i), or take i be reference and increment it (decrement in the case of the last element)

[Prasad H L Bhat (hlprasu)]

The code is now fixed according to this wish list.