hide cursor during startup

During application startup,it will always draw the mouse cursor based on the coordinates it receives.

In src/gui/embedded/qwscursor_qws.cpp, if we add setCursor(QWSCursor::systemCursor(Qt::BlankCursor)) instead of setCursor(QWSCursor::systemCursor(Qt::ArrowCursor)), it will hide the cursor during application startup.
To keep it hidden the application must call
QApplication::setOverrideCursor(Qt::BlankCursor);
Otherwise the cursor returns when the mouse is moved.

Please validate if the change is OK for the embedded linux Qt 4.8.2 open source version.