Make the code compile with both Qt4 and Qt5.
Write Qt settings to lxqt.conf instead of the deprecated Trolltech.conf in Qt5.
Show cursors by using raw xcb calls since Qt5 does not support creating QCursor based on native cursor handle.
Rename lxqt-config-cursor to liblxqt-config-cursor since it's a library.
Add <OnlyUnallocated /> to lxqt-config.menu to avoid duplicated items in "Other Settings" section.
This fixed lxde-qt bug #186.
Avoid putting system programs in "LXQt settings" category since they belong to "System settings".
Fixes layout on the Fonts Config Ui

Now everything stay in place when resizing the dialog.
Fix missing libxcb linking so building with llvm/clang now works.
Fix bug #242: lxqt-config-input: Mouse acceleration & sensitivity settings are not saved.
Use QWindow::windowHandle()->winId() to replace QWidget::winId() due to a bug of Qt5.