wayland: Support for QtWayland touch input events

When running with QtWayland (qmlcompositor) as Wayland server,
touch inputs are reported via the qt_touch_extension protocol.

The files wayland-qt-touch-extension.{c,h} are auto-generated
from the XML definition src/extensions/touch-extension.xml in
qtwayland (git://gitorious.org/qt/qtwayland.git).