annotation CHANGE WIP parsing XML attributes as YANG metadata annotations

Interconnect XML attributes in data tree with the corresponding metadata
annotation (implemented as a YANG extension plugin).

Still proof of concept with only type processing, not tested so far.
diff --git a/src/tree_schema_compile.c b/src/tree_schema_compile.c
index 8f6bbf4..25b16e4 100644
--- a/src/tree_schema_compile.c
+++ b/src/tree_schema_compile.c
@@ -6701,7 +6701,9 @@
                     LY_CHECK_ERR_GOTO(r = lysp_stmt_parse(ctx, stmt, stmt->kw, &parsed), ret = r, cleanup);
                     LY_CHECK_ERR_GOTO(r = lys_compile_type(ctx, ext->parent_type == LYEXT_PAR_NODE ? ((struct lysc_node*)ext->parent)->sp : NULL,
                                       flags ? *flags : 0, ctx->mod_def->parsed, ext->name, parsed, (struct lysc_type**)compiled,
-                                      units && !*units ? units : NULL), ret = r, cleanup);
+                                      units && !*units ? units : NULL), lysp_type_free(ctx->ctx, parsed); free(parsed); ret = r, cleanup);
+                    lysp_type_free(ctx->ctx, parsed);
+                    free(parsed);
                     break;
                 }
                 /* TODO support other substatements (parse stmt to lysp and then compile lysp to lysc) */