Add SpinBox::inputMethodComposing

Change-Id: I5c2b10cf293b36547486a12f6a50e8083d36c6a3
Reviewed-by: Liang Qi <liang.qi@digia.com>
Add ComboBox::inputMethodComposing

Change-Id: I3701a28721252bc3cca46a223bb665faf38002f7
Reviewed-by: Liang Qi <liang.qi@digia.com>