Previously used x11 plugin does not compile with Qt5, because Qt5 does not use Xlib, it uses xcb. Rewrite screen capture plugin from Xlib to xcb.
I made xcb libs compile required dependency, but availability of X shared memory extension is checked at runtime. It is used to effectively get image pixels data, instead of transfering 8Mb over the wire. Xdamage is used to limit image getting operations only within actually changed rectangles of screen.
Related bug: https://bugs.kde.org/show_bug.cgi?id=377998