Remove function comparison from label iteration

Remove function comparison from label iteration

We already have filtered functions and inlines, so just iterate in each
of those to look for labels.

* dwflpp.cxx (dwflpp::iterate_over_labels): Assume that the die we're
  looking at is already a matching function, and don't descend into
  inlined functions in this body.
* tapsets.cxx (query_srcfile_label): Iterate through inlines too.
  (query_cu): Iterate over functions and inlines instead of the CU.