Adds a class for ftrace marking program flow of KWin. This used in conjunction
with a tool like GPUvis can be very powerful.
I use it at the moment for analyzing the compositing behavior of KWin on X11.
For this I also apply a patch to the XServer adding the same capability.
Besides the class also some marking points have been added. Ftracing can be,
if it has been built into the binary, activated via D-Bus or per env var
KWIN_PERF_FTRACE directly from the start.
Example ftrace in GPUvis