Refs #100890  Stub nametree module.
Refs #100890  Refactor flatname support into its own module.

It is useful for more than just btrees.
Refs #100890  Skiplist implementation for new nametree module.

This code is based largely on the version of ccnr_store.c found in
188c53f24ca36b3ae31c2c1d90f210e04e74be5a
which was before the btree-based index was introduced.
Refs #100890  Add some doxygen comments.
Refs #100890  Try using something shorter than ccn_nmentry.

Since this ideally will be generic for both cobs and interests (and
conceivably other things), try out ccny (short for ccn any).
Refs #100890  Make names more generic.
Refs #100890  Add prev links to nametree, so we can reverse-search.
Refs #100890  Deps.
Refs #100890  Remove a level of indirection - allocate skiplinks as part of struct.
Refs #100890  Add a nametree test, fill out api, fix bugs found.
Refs #100890  Add ccn_nametree_destroy().
Refs #100890  Introduce CCN_STRICT_PREFIX define for special compare result.
Refs #100890  Add some disabled-by-default leak detection code to nametreetest.
Refs #100890  Add some comments describing what a nametree entry (struct ccny) is for.
depends
Refs #100890  Use a sentinel node to head the skiplist and reverse list.
Refs #100890  Fix bugs in initialization, and prev link updates.
Refs #100890  Change nametree api for dealing naturally with disconnected entries.

Also added entry count and handling for cookie collisions.
Fixed some nasty use-after-free bugs noticed along the way.
Refs #100890  Add ccn_nametree_grow()
Refs #100890  Maintain a recommend nametree limit so client can grow or trim.