b_tree: No need to shift half the leaf when erasing.
b_tree: Specialize key_ops for sizeof(Key) <= sizeof(Key *).
b_tree: Simplify split_insert a bit.
b_tree: Only verify order invariant when !TPIE_NDEBUG.
b_tree.h: Add comments describing some of the helper classes.
b_tree: Remove unused b_tree_block::erase.
b_tree: Remove unused bfs_order_block_dump.
b_tree.h: Add file-level docstring.
b_tree: Log whenever the tree height changes.
b_tree: Document in_order_dump.
b_tree: Add some method-level documentation.
b_tree: Refactor, adding b_tree_leaf::index_of.
b_tree: Add b_tree::try_find and b_tree::find.
Update test/b_tree program to use a more advanced Value class.