QToolbar should fill available width on Symbian

The native Symbian toolbar always scales the buttons to fit the full width of the screen.

However, the QToolbar implementation only makes the buttons as large as they need, usually resulting in a toolbar that doesn't have the required width or is too large. This doesn't fit to the phone design. Additionally, it doesn't look good - toolbars also take the full width on other phone platforms where a small screen is used.

Proposed solutions: QToolbar should scale buttons to always use full available width by default on Symbian. Optionally provide an option to control this behavior manually.

Attached screenshot that compares native toolbar and QToolbar in landscape and portrait mode.
Attached test app that constructs a simple QToolbar and demonstrates layouting issues.