Test for filename triplet sanity in rpmfiNew()

Test for filename triplet sanity in rpmfiNew()

- Basename and dirindex counts must be equal, dirnames count must be
  larger than zero and no larger than number of basenames. Check
  that directory indexes are within range.
- There are mountains of further checks to be added here (and elsewhere)
  but we gotta start somewhere... and filename triplets are one of the more
  critical elements we got.