Until this commit Items with a size of 1 could be rounded to
bounds with a size of 0 or 2 due to floating point errors, leading
to slightly too large or disappearing items. The new approach
preserves the size of items.

An animated drag operation will now stop if the user interacts with
the content area again before the animation is finished. It is also
stopped if the user interacts with the scrollbars.

Previously, positioning such an item would hang while trying to find an
appropriate position for the item, because no position in the grid was
suitable, and implicit cells in the layout direction would be added
until a viable position was found.

We now ensure that there are enough cells in the cross direction to hold
each of the auto-placement items before trying to position those items.

The TextHolderComponent and Viewport::componentHolder don't have any
accessible semantics, so they shouldn't be included in the accessible
component hierarchy.

The TextHolderComponent and Viewport::componentHolder don't have any
accessible semantics, so they shouldn't be included in the accessible
component hierarchy.

Some Windows 11 devices have both touch screens and mouse inputs, and
these can be used simultaneously.

The Viewport (and ListBox) now check the input source of each mouse
down. If the source is not a mouse, the viewport will always enter
drag-to-scroll mode, regardless of the result of isScrollOnDragEnabled.

Negative indices should count backwards from the last explicit
row/column number. If the resulting line number would appear before
the first explicit row/column, implicit grid lines should be added
before the first explicit row/column.

Previously, a touch on a component outside the Viewport would interrupt
and cancel a scroll gesture inside the Viewport.

Now, the Viewport will respond to all drag events from the input source
that started the drag, allowing the Viewport to be scrolled with one
input source while adjusting other controls with another input source.

The FontsDemo is useful for testing this behaviour, as it has two
Viewports on a single screen, along with some other controls.

See BREAKING-CHANGES.txt for more details.

This fixes warnings that are emitted when building with the `-analyze`
flag enabled.