Cleanup QtWidgets examples:
- use nullptr (clang-tidy)
- use member-initialization
- adjust the style
- fix includes
Change-Id: Ic5448606aacc525ea60b615a69227017aa2b821a
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Several of the examples were not even working besides using deprecated
classes.
Change-Id: I352e0629d490593edcc5868d2ec5a8ff222eaeab
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>