[augeas-devel] Simplify handling of path expressions

[David Lutterkort]

This series of patches considerably simplifies the evaluation of path
expressions and searching/iterating in the tree. The two big changes are that

(1) tree nodes now have an explicit 'parent' pointer

(2) root nodes of a tree now point back to a fake parent (called 'origin'),
    i.e. the tree is now edge-labeled

These patches clean up a good deal of ugliness in handling path
expressions. In particular, the paths that are generated when a tree is
printed are now much more correct ;)

David