validation NEW when validation

Integrated only into XML parser for now.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index e48cb18..8023c2b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -229,7 +229,8 @@
     src/plugins_types.c
     src/plugins_exts.c
     src/xml.c
-    src/xpath.c)
+    src/xpath.c
+    src/validation.c)
 
 set(lintsrc
     tools/lint/main.c