Adapt window to new form size

Window size will be adjusted to fit an opened form with the "resetFormSize" Form style.

GDC tries to maintain the current window size. The window grows only if new content can't fit in the current size, and the GDC never shrinks a window. This is generally the best behavior, as you don't expect window size to jitter each time you change the content. Nevertheless, in the 4GL context of OPEN FORM ... DISPLAY FORM, it may make sense to shrink the window to the size demanded by the newly opened form, particularly if the new form is really small and you don't want to have a large window with lots of empty space. You can use the new "resetFormSize" form style attribute to indicate that the window must adapt its size to the newly opened form.
<Style name="Form.f1">
  <StyleAttribute name="resetFormSize" value="1" />
</Style>