Improve size hints for SpinBox and TextField

These were both too small on most platforms.
Since we have rather broken logic in widgets for this,
I will simply assume they share the same height.

Change-Id: I98da5a925087fec300de3c1c91b58110103e1a38
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Pass selected tab rect to style

In particular QGtkStyle depends on having the selected tab rect
in the style option. Otherwise it cannot draw the tab frame
correctly as we pass this information on to gtk.

In addition we were not correctly setting the tab position on
the frame.

Change-Id: I9aa17d6b33f6b283122014994dc92a6afb913f30
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Style polish

Adding the right margin of TableView and adding some extra margins
makes the example look a bit more polished

Change-Id: If969230fe2e1068a42f92708df311550f88fb060
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>