Merge branch 'box-tree_indexes-speedup' into unstable

* box-tree_indexes-speedup:
  [box] build_indexes: malloc 20% more
  [box] build_indexes: separate arrays building from trees building
  [box] cosmetic changes: rename str_tree to tree
  [box] don't use find and find_by_tuple in tree indexes
  [box] save index key inside tree_index_member (in place)
  [sptree] update
  [core] do prelease after initialization
  [box] indexes speedup 	* build tree indexes after full loading 	* save in tree index parsed key (not only tuple) 	* lexicographical order in tree
  [sptree] fix initialization from array of one element