bugfix: ZoomView didn't set output dirty on ContentChanged
switched to xinput2
added support for Pen, Finger, and Mouse pointer events
added PointerSignalFilter
made ZoomView finger-draggable
switched back to X11 (no xcb anymore)
split PointerSignalFilter into .h and .cpp
new signals Pen{In,Out}, ZoomView reacts on them
added methods to map/unmap to Texture
bugfix: uninitialized point in ZoomView
made Texture keep buffer data
added class Buffer representing device memory and Texture support to load from it
reverted ZoomView to mouse-controlled operation
decreased verbosity of XWindow
bugfix: Window didn't register for ContentChanged signals
added Pen{In,Out} signals to PointerSignalFilter
throw exception in Buffer when glGenBuffers doesn't succeed
added OpenGl guard to Window's destructor
added skia_pixel_t and its OpenGl traits
added opengl guard to buffer destructor