Comment # 8 on bug 972787 from Egbert Eich

Lately, we have been getting numerous issues regarding subsystems which need to
run during login to a desktop session.
The startup scripts are part of xdm or xinit, the subsystems however are not
part of X11:XOrg. 

I will therefore start moving these pieces out of the main startup script and
add support for subsystem provided (and supported) scriptlets instead. This
way, we don't have to support a wide range of versions of the respective
subsystem with our scripts which bloats the code unnecessarily.