SpinBox: attempt to fixup the input as appropriate

So for example "-0", which is a valid intermediate value, becomes
"0" when the spinbox is accepted (enter) or it loses focus.

Task-number: QTBUG-34774
Change-Id: Ie153294755aae2bf94ba1cb53c40a8fc5f1f5862
Reviewed-by: Liang Qi <liang.qi@digia.com>
Make scrolling on combobox work

Handles mouse scrolling event over combobox - scrolling up does the same
as pressing up arrow and scrolling down equals pressing down arrow.

Change-Id: I67adef46f201c0d4c88dabd5a717effc8f1e909d
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: David Edmundson <davidedmundson@kde.org>