Document sed bug.

cfg-ml-pos.in

@@ -12,6 +12,7 @@ if [ -z "${with_multisubdir}" ]; then
   multisubdir=
 else
   multisubdir="/${with_multisubdir}"
+  # The '[^/][^/]*' appears that way to work around a SunOS sed bug.
   dotdot=`echo ${with_multisubdir} | sed -e 's:[^/][^/]*:..:g'`
   # TOP is used by newlib and should not be used elsewhere for this purpose.
   # MULTITOP is the proper one to use.