Merge branch 'hn/reftable-coverity-fixes'

Merge branch 'hn/reftable-coverity-fixes'

Problems identified by Coverity in the reftable code have been
corrected.

* hn/reftable-coverity-fixes:
  reftable: add print functions to the record types
  reftable: make reftable_record a tagged union
  reftable: remove outdated file reftable.c
  reftable: implement record equality generically
  reftable: make reftable-record.h function signatures const correct
  reftable: handle null refnames in reftable_ref_record_equal
  reftable: drop stray printf in readwrite_test
  reftable: order unittests by complexity
  reftable: all xxx_free() functions accept NULL arguments
  reftable: fix resource warning
  reftable: ignore remove() return value in stack_test.c
  reftable: check reftable_stack_auto_compact() return value
  reftable: fix resource leak blocksource.c
  reftable: fix resource leak in block.c error path
  reftable: fix OOB stack write in print functions