1.0.29.21: less strict os-provides-dladdr.c

1.0.29.21: less strict os-provides-dladdr.c

* Allows us to use dladdr on FC6, where previous test failed because
  we expected an exact match on the name for "printf", whereas the
  name we got is "_IO_printf".

  IIRC the reason for the name was that some marginal platform had a
  dladdr that always returned "unknown function" or something like
  that -- here's hoping that's not the case anymore, but if it is,
  testing that the return value is not a placeholder string like that
  is probably better.