QSqlTableModel::removeRows() doesn't work consistently with QAbstractItemModel.

I've written a small demo application demonstrating the bug. Calling
insertRows(1, 2) on the QSqlTableModel inserts two rows into the model - as
expected. But calling removeRows(1, 2) right afterwards only removes one of the
previously inserted rows.

I'm either fatally wrong here or this is at least inconsistent with what
QAbstractItemModel defines, if not a bug in QSqlTableModel.