Qt5 related changes

1. QCursor constructor needs QPixmap instead of const char*
2. Qt::WFlags obsoleted. Replaced by Qt::WindowFlags
3. QPixmap::serialNumber() deprecated. Replaced by QPixmap::cacheKey()
4. QVariant(Qt::GlobalColor) is now private. Use QVariant(QColor(Qt::GlobalColor)) instead.
5. QMetaMethod::signature obsoleted. Replaced by QMetaMethod::methodSignature().
6. QDir::convertSeparators obsoleted. Replaced by
   toNativeSeparators/fromNativeSeparators
7. QRegion::unite deprecated. Replaced by QRegion::united
8. QCoreApplication::UnicodeUTF8 is deprecated.

Change-Id: I44861d866aa2b2b5cb339b620c120a0c075ffd55