The immutable sorted string table library project, mtbl 1.3.0,
was released. This release includes improvements enabling
aggregation. In detail:

 * Fix mtbl_reload_now() on filesets with open iterators.
 * Add support for absolute pathnames in filesets
 * Make merge function an optional parameter for mergers and filesets
   to enable unmerged results.
 * Add dupsort function to sort unmerged results based on data.
 * Add filename filter option to filesets. This provides functionality
   similar to mtbl_fileset_partition() but resilient against fileset
   reloads.
 * Add mtbl_fileset_dup() to open an existing fileset with different
   options.