The king is dead, long live the king. KScreen no longer links against libX11.

As part of the porting I also moved the components which are shared between
XRandR and XRandR1.1 backends to the backends directory, renamed them and
wrapped the tools in xcbwrapper.h into XCB namespace.

The XCB::Wrapper class is now also more versitile, thanks to some C++11 template
magic it can now wrap arbitrary xcb structs and calls with arbitrary number of
arguments. XCB::ScopedPointer is also available to prevent leaks.