minor, provide tool (rotz-combine) to combine several tags into one, making them aliases of one another

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'cmd/combine' into next

* cmd/combine:
  minor, provide tool (rotz-combine) to combine several tags into one, making them aliases of one another
minor, provide rotz-rename, a tool to rename tags

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'cmd/rename' into next

* cmd/rename:
  minor, provide rotz-rename, a tool to rename tags
Merge branch 'next'

* next:
  minor, provide rotz-rename, a tool to rename tags
  minor, provide tool (rotz-combine) to combine several tags into one, making them aliases of one another
  minor, upon rem_vertex() traverse the alias list and unput_vertex() every alias
  minor, treat vtxkey space as aka-list even for the very first entry
  minor, use vtx-id -> name mapping for the alias list instead of another namespace
  fix, actually remove the vertex-name->id lookup upon rotz_rem_alias()
  minor, support tag alias deletion via --delete|-d in rotz-alias
  minor, support rotz-alias TAG to display all aliases of TAG
  minor, provide rotz_get_aliases()
  minor, put aliased vertex before checking alias list in rotz_add_alias()
  fix, PEBKAC, when rem'ing from alias buffer actually delete the \nul byte too
  minor, provide rotz-alias tool
  minor, provide rotz_rem_alias() and friends
  hygiene, like add_vertex() is really put+rnm, split up rem_vertex() into unput+unrnm
  minor, introduce aliases
  hygiene, document that we can't keep the separation promise for iterators
  hygiene, separate strictly between tokyocabinet routines and our routines that hand out keys and know about the inerts