Log Message:
graphics/kvantum: update to 0.19.0

-Allow dragging from some disabled widgets.
-Added an option (to Kvantum Manager) for setting the toolbar icon size to the
font height if possible.
-Don't style vertical toolbars because, otherwise, they might look ugly.
-Always check if the drag manager is deleted after it sends mouse events (to
prevent any crash).
-Increased the drag distance and delay when dragging is done from buttons.
-Try to do less calculations to get widget sizes by not consulting QCommonStyle
as far as possible.
-Draw view-items independently of QCommonStyle to apply all size settings
correctly.
-Always reserve the vertical space for a single-line text in view-items.
QCommonStyle is inconsistent in this regard and may create a tiny item editor
when the text is empty. Qt doesn't give enough info to QStyle for knowing
whether the editor is active.
-Ignore a view-item's custom brush when it's selected (as QCommonStyle does).
-Cleaned up the code of transient scrollbar animation (and fixed a rare case,
where a transient scrollbar might not disappear after app startup — as in
kcharselect).
-Fixed a small problem in (Krita's) KisSliderSpinBox.