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/src/context.c b/src/context.c
index 9de0592..d01f4f7 100644
--- a/src/context.c
+++ b/src/context.c
@@ -47,7 +47,7 @@
     uint8_t implemented;
     LYS_INFORMAT format;
 } internal_modules[LY_INTERNAL_MODS_COUNT] = {
-    {"ietf-yang-metadata", "2016-08-05", (const char*)ietf_yang_metadata_2016_08_05_yang, 0, LYS_IN_YANG},
+    {"ietf-yang-metadata", "2016-08-05", (const char*)ietf_yang_metadata_2016_08_05_yang, 1, LYS_IN_YANG},
     {"yang", "2017-02-20", (const char*)yang_2017_02_20_yang, 1, LYS_IN_YANG},
     {"ietf-inet-types", "2013-07-15", (const char*)ietf_inet_types_2013_07_15_yang, 0, LYS_IN_YANG},
     {"ietf-yang-types", "2013-07-15", (const char*)ietf_yang_types_2013_07_15_yang, 0, LYS_IN_YANG},