tree - N-ary tree
=================

Genaric N-ary tree, it is designed to be wrapped in more high level and specialized datastructure.

Data structures
---------------

* `tree`
+
--
Represents a tree node.

`next`::
    Pointer to the next node.

`parent`::
    Pointer to the parent node.

`child`::
    Pointer to the first child.

NOTE: Only members related to the tree are defined, no pointer to the associated data. +
      That is because it is designed to be flexible and expected to be built upon (included in another structure).
--

Functions
---------

`tree_new()`::

    allocates memory of a `tree` structure.

`tree_link()`::

    Links the root of 'tree' to be a child of 'parent'. +
    Those linking the two tree's togheter.

`tree_unlink()`::

    Removes the node 'tree' from the entire tree. +
    The children of 'tree' is relinked to exist under 'tree'->parent.

`tree_move()`::

    Moves the subtree 'src' to exist as a child to 'dst'.

`tree_detach()`::

    Detaches the subtree pointed by 'tree'. and creates two tree's.

`tree_traverse()`::

    Traverses the tree applying 'fn' on every node.

`tree_parent_count()`::

    Returns the number of parent 'tree' has.

`tree_is_root()`::

    Returns nonzero if node is root (has no parent and no next), zero otherwise.
+
NOTE: this may be implemented as a macro.

`tree_is_leaf()`::

    Returns nonzero if node is leaf (has no children), zero othersize.
+
NOTE: this may be implemented as a macro.