Description of problem:

I am trying to launch matchbox-window-manager (alien rpm) from /usr/bin/startx 
and found out about the new Xclients.d facility described in #142260. Looking 
around a bit I can't seem to find a way to get this facility working with 
startx. The default /etc/X11/xinit/Xclients script does not source 
my /etc/X11/xinit/Xclients.d/Xclients.mb.sh like /etc/X11/xinit/Xsession 
does.

Version-Release number of selected component (if applicable):
xorg-x11-xinit-1.0.2-9.fc6

How reproducible:
Always

Steps to Reproduce:
1. Make sure you do not have any window manager or desktop installed.
2. install matchbox-window-manager
3. create a window manager startup script in /etc/X11/xinit/Xclients.d 
# cat > /etc/X11/xinit/Xclients.d/Xclients.mb.sh
/usr/bin/xterm &
exec /usr/bin/matchbox-window-manager
^D
3. start x window with startx
# startx
  
Actual results:
X does not start

Expected results:
X starts and launches an xterm and the matchbox window manager