WelcomeMode: Remove unused code

The "platform" function is not used in QML, so let's remove it. In case
it will be needed at some point in time, better use Qt.platform

Change-Id: Ie9cecf8f2953934fbe8b0bb16f2267975af30fd0
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
Theme: Remove theme_p.cpp

Merge into theme.cpp

Change-Id: I2068f224e6364a87573fe7e938d4dd8089cbaafa
Reviewed-by: hjk <hjk121@nokiamail.com>