Correctly remember checkboxes on Continue Later (WB)

Correctly remember checkboxes on Continue Later (WB)

The WinBoard tournament dialog could be left in an inconsistent state
on Continue Later, when the user untickedthe checkboxes for auto-stepping
and two games per line, after on an earlier attempt their ticking had
already resulted in settng the line/position index to a negative value.
Negative values left in the numeric entriesare now reset to 0 when the
chackboxes are unticked.