YANG sub module linking + unsupported yang construct + defect fix

Change-Id: I224c8c14ee2111f6844278cb540c48651544f59b
diff --git a/utils/yangutils/src/test/resources/EnumBoundaryValue.yang b/utils/yangutils/src/test/resources/EnumBoundaryValue.yang
new file mode 100644
index 0000000..ac87ef0
--- /dev/null
+++ b/utils/yangutils/src/test/resources/EnumBoundaryValue.yang
@@ -0,0 +1,16 @@
+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    leaf ifType {
+        type enumeration {
+             enum "unbounded";
+             enum ZERO;
+             enum two;
+             enum four;
+             enum seven {
+                 value 21474836472147483647;
+             }
+         }
+     }
+}