use xcb-screen count instead of qguiapplication.screens

Review Request #122320 - Created Jan. 29, 2015 and submitted - Latest diff uploaded

Nick Shaforostoff
graesslin, luebking

this patch makes kcminit behave like in kde4: it uses proper xcb screen count which may be different from QGuiApplication::screens().count().

for example when i connext external monitor via vga to my laptop, xcb screen count is still '1', while QGuiApplication::screens().count() returns '2'.

switching from QGuiApplication to QCoreApplication still wasn't possible because modules like 'mouse' need gui initialized and would crash if kcminit uses QCoreApplication.

i have built kcminit on ubuntu vivid alpha 32-bit, replaced binaries and libraries in the system and successfuly could run kcminit_startup and reboot also went fine.