path FEATURE new compiled path structure (#1108)

Refactoring includes using it for
instance-identifier and for checking leafref,
it is evaluated using stanrad XPath. Predicates
used for lyd_new_list2(), tests included.
diff --git a/tests/utests/data/test_tree_data.c b/tests/utests/data/test_tree_data.c
index ecba711..0a1075c 100644
--- a/tests/utests/data/test_tree_data.c
+++ b/tests/utests/data/test_tree_data.c
@@ -1,4 +1,4 @@
-/*
+/**
  * @file test_tree_schema.c
  * @author: Radek Krejci <rkrejci@cesnet.cz>
  * @brief unit tests for functions from tress_data.c