New which_lib.c

[Nicola Pero]

I've rewritten which_lib.c to issue the recurrent bug/problem report about
it picking up some obvious inappropriate library (last report by Helge
some months ago I think, whose mail I unfortunately lost, but I remember
what the problem was).

Basically, before which_lib was traditionally doing the following -

 for each dir in the library search paths,
  {
   if there is a perfectly matching lib in that dir, use it;
   if there is an approximate matching lib in that dir, use it;
   if shared && if there is any shared lib with that name in that dir, use it;
   if there is any static lib with that name in that dir, use it;
  }

this is very unsatisfactory, because if you ask for a shared non-debug
non-profile library, but you have a static profile debug version in the
first library search path, it will be used, even if the second library
search path perhaps contained precisely the required library !

That used to periodically upset someone ... hopefully no longer, because
now which_lib is doing the much more logical -

 for each dir in the library search paths,
  {
   if there is a perfectly matching lib in that dir, use it;
  }

 for each dir in the lirbary search paths,
  {
   if there is an approximate match in that dir, use it;
  }

 for each dir in the lirbary search paths,
  {
   if shared && if there is any shared lib with that name in that dir, use it;
  }

 for each dir in the lirbary search paths,
  {
   if there is any static lib with that name in that dir, use it;
  }

The `approximate match' has also been improved considerably, it should be
pretty intelligent now.

The thing might probably still be a bit buggy, as I have rewritten the
whole lot, but I have to leave it alone now as I have other more high
priority stuff at work to do.

Please let me know of any problems with the new which_lib, I'll address
them tomorrow or in the next days.