QItemSelectionModel::is[Row|Column]Selected(): Make this more efficent by only checking ranges for the requsted row/column

QItemSelectionModel::is[Row|Column]Selected(): Make this more efficent by only checking ranges for the requsted row/column. Currently when it goes over each column/row to find out if all the items in that row/column are actually selected, it does this for every single possible range in the list. It could be more efficent if the list of ranges was preprocessed first to only contain the row/column that is actually being checked against.