QAbstractSpinBox::inputMethodQuery(): Consider input method hints set on the spin box.

The derived classes (QSpinBox, QDoubleSpinBox, QDateTimeEdit, QTimeEdit)
set various input method hints on the spin box in the init() methods
of their private classes which did not have any effect since
QAbstractSpinBox::inputMethodQuery() was implemented to return the
hints of the embedded QLineEdit only. Change it so that hints set
on the QAbstractSpinBox are also considered.

Change-Id: I76b7c4d3e0869589c110cf3a0b2c3f94201db5d5
Reviewed-by: Andy Shaw <andy.shaw@theqtcompany.com>
Reviewed-by: Liang Qi <liang.qi@theqtcompany.com>