dtlogin|Xsession/config: setup some env variables and fontpath for linux (and CSRG) systems.

What we really need are more fonts installed, like all of the xf 75dpi
and 100dpi fonts.  100dpi looks much better than 75/72 dpi, especially
on any display larger than 1024x768.  Of course, in the far future, we
should use the anti-aliased TT fonts everyone else uses these days
anyway.

cde/programs/dtlogin/config/Xsetup.src

@@ -56,6 +56,8 @@ fi
 
 #ifdef sun
   XDIR=/usr/openwin/bin
+#elif defined(CSRG_BASED) || defined(linux)
+  XDIR=/usr/bin
 #else
   XDIR=/usr/bin/X11
 #endif