git ignore: add pattern for .redo/
lib/tree: rename leaf_item_ptr to leaf_data_ptr
lib/tree: use fast binary search for node item lookups
lib/tree: add notes regarding binary search within nodes
lib/tree: adjust tree_insert split failure message
lib/tree: move tree_find_root to node_find_root
lib/tree: use ASSERT_BRANCH, ASSERT_LEAF
lib/tree: move ASSERT_ROOT into node.h
lib/tree: add note about hypo binary search
lib/tree: reorder node functions logically
lib/tree: add node_first_key, branch_search_addr