Merge branch 'refs/heads/t/sha3' into master

This code was written long ago and was sitting in a development branch
for some years. As such it was part of the pu branch and so has seen
some testing.

There's an easy conflict in fsck.c where one side added a function
parameter and the other renamed some variables.

* refs/heads/t/sha3:
  Version 3 tables.
  Add sha3 implementation, introduce version-2 tables.
  Prepare hash_function() for multiple hash algorithms.
  Store table version in struct osl_table.
  Initialize column name hash *after* table version is known.
  osl_open_table(): Remove pointless directory check.
  Remove sha1.h.
  Remove COMPAT_TABLE_VERSION.