extensions CHANGE WIP implementation of Metadata annotations

The first proof of concept implementation - not only for the metadata
extension. but also of the extension instance compilation mechanism. It
is not yet tested, only type substatement is processed to verify the
implementation by metadata in XML data.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9b325cc..b5cd34c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -220,6 +220,7 @@
     src/tree_schema_helpers.c
     src/parser_yang.c
     src/parser_yin.c
+    src/parser_stmt.c
     src/printer.c
     src/printer_schema.c
     src/printer_yang.c