SIZEPOLICY attribute removal for containers

The SIZEPOLICY attribute is no longer available for layout containers like TABLE / GRID.

Before version 2.40 it was possible to specify a SIZEPOLICY attribute for several types of form elements, including containers such as TABLE, GRID. The SIZEPOLICY attribute makes no sense in containers and is only meaningful for leaf nodes (widgets such as EDIT, COMBOBOX). The form compiler will now report a syntax error if the SIZEPOLICY attribute is used in the definition of elements that are not widgets.