Revision 1515088

On the log-addressing branch:  For low-overhead checksumming,
add standard FNV-1a and a faster modified version of that to
the list of checksum kinds supported with svn_checksum_t.

We will use this new checksum to secure parts of FSFS (and
later FSX) that are not directly covered by MD5/SHA1 content
checksums.  That will help to localize corruptions much quicker
and more accurately but it will not eliminate the need to run
a full content verification.

* subversion/include/svn_checksum.h
  (svn_checksum_kind_t): add new checksum types

* subversion/include/private/svn_subr_private.h
  (svn_checksum__from_digest_fnv1a_32,
   svn_checksum__from_digest_fnv1a_32x4): new ultility API
  (svn__fnv1a_32,
   svn__fnv1a_32x4): APIs directly create checksums

* subversion/libsvn_subr/fnv1a.h
  (): new file
  (svn_fnv1a_32__context_t,
   svn_fnv1a_32__context_create,
   svn_fnv1a_32__update,
   svn_fnv1a_32__finalize): declare lib-private API to calculate
                            FNV-1a iteratively
  (svn_fnv1a_32x4__context_t,
   svn_fnv1a_32x4__context_create,
   svn_fnv1a_32x4__update,
   svn_fnv1a_32x4__finalize): declare lib-private API to calculate
                              modified FNV-1a iteratively

* subversion/libsvn_subr/fnv1a.c
  (): new file
  (FNV1_PRIME_32,
   FNV1_BASE_32): FNV1 constants
  (fnv1a_32): FNV-1a core algorithm
  (SCALING,
   fnv1a_32x4,
   finalize_fnv1a_32x4): modified FNV-1a core algorithm
  (svn__fnv1a_32,
   svn__fnv1a_32x4): expose API to directly calculate checksums
  (svn_fnv1a_32__context_t): define stream context structure
  (svn_fnv1a_32__context_create,
   svn_fnv1a_32__update,
   svn_fnv1a_32__finalize): implement
  (svn_fnv1a_32x4__context_t): define stream context structure
  (svn_fnv1a_32x4__context_create,
   svn_fnv1a_32x4__update,
   svn_fnv1a_32x4__finalize): implement

* subversion/libsvn_subr/checksum.c
  (fnv1a_32_empty_string_digest_array,
   fnv1a_32x4_empty_string_digest_array): new constants
  (empty_string_digests,
   digest_sizes): add entries for the new checksums
  (svn_checksum__from_digest_fnv1a_32,
   svn_checksum__from_digest_fnv1a_32x4): implement new constructors
  (DIGESTSIZE,
   validate_kind,
   svn_checksum_create,
   svn_checksum__from_digest_fnv1a_32,
   svn_checksum__from_digest_fnv1a_32x4,
   svn_checksum_match,
   svn_checksum_to_cstring_display,
   svn_checksum_to_cstring,
   svn_checksum_serialize,
   svn_checksum_dup,
   svn_checksum_empty_checksum,
   svn_checksum_is_empty_checksum): support the new checksum kinds by simply
                                    extending ranges and switch statements
  (svn_checksum,
   svn_checksum_ctx_create,
   svn_checksum_update,
   svn_checksum_final): support the new checksum kinds by calling the new
                        private fnv1a* functions

* subversion/tests/libsvn_subr/checksum-test.c
  (test_checksum_parse): add tests for fnv1a*
  (test_checksum_empty,
   zero_match,
   zero_cross_match): cover new checksum kinds by simply extending
                      the loop ranges