The current look and feel on iOS (with the default Base style)
is terrible. This commit alone doesn't change anything, but it
allows us to do minor iOS-specific tweaks that will greatly
improve the usability on iOS already in Qt 5.4.

Change-Id: I86764dd92bdfaae8170a8cd6709177a9a064cda8
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>