file based on the previous list of directories stored there which
should overcome a weakness of the '-m' switch which can only add
libs. This is an ideal way of updating the hints list after adding
or removing a shlib since it will remove entries that are gone and
doesn't need to have all the directories spelled out each time.
(eg: rm -f /usr/lib/libtcl75*; ldconfig -R) This only works for
version 2 hints files (which we've been generating for a year or
so) which store the path.