* XPath parser: fixing lexical issues cornercases

* Some complexities in Section 3.7 Lexical Structure of XPath 1.0 spec
  * There used to be some cornercases where function-names could not be used as nodes
  * For example, `node()` is a nodetest, so `/node/` caused an error.
  * In the grammar these include: axisnames,  nodetests, functionnames
  * The NCNames vs functionnames is now impölemented according to the lexical structure section

lib/src/clixon_xpath.c

@@ -160,6 +160,11 @@ axis_type_int2str(int axis_type)
     return (char*)clicon_int2str(axis_type_map, axis_type);
 }
 
+int
+axis_type_str2int(char *name)
+{
+    return clicon_str2int(axis_type_map, name);
+}
 
 /*! Map from xpath_tree node name int to string
  */