Q*Application classes have unusually many static functions. In many
cases in our code, these functions are unnecessarily called as instance
functions, using the qApp helper.

This patch replaces many occurencies of qApp with the according
Q*Application classname.

Change-Id: I6099a419fa7bf969891269c37ed7a9e817ef5124
Reviewed-by: hjk <hjk@qt.io>