Fixes for issue #2391
Merge branch 'v1.13.x' into sam_2563
Made error messages not use "argument(s)".
Merge branch 'sam_2537' into sam_2563
Check if result is null before looking for _next
Merge branch 'sam_2537' into sam_2563
Merge branch 'sam_2537' into sam_2563
Merge branch 'sam_2537' into sam_2563
Made metadata_persistence superblock magic be version-templatized.
Smartened up the cluster_metadata_magic_t and auth_metadata_magic_t templates.
Made write_blob use LATEST, read_blob take a parameter, still with use of ONLY_VERSION in persist.cc.
Gave write_blob_t a vanity cluster_version_t parameter.
Removed pointless member pointer parameter to persistent_branch_history_manager_t.
Removed RSI comment about previous commit.
Made auth_metadata_superblock_t capable of reading with older version -- it can now withstand serialization version upgrades.
Removed use of uninitialized field_name member pointer field, removed that field (see recent commits).  Made use of write_metadata_blob, read_branch_history_blob functions, etc.
Added actual bring_up_to_date calls, as is appropriate.
Removed RSI comment.
Added btree_sindex_block_magic_t, moved sindex_block_version to cc file.
Removed weird whitespace after __attribute__ keywords...