Build with libyang

Change-Id: Ib2f0b94c7782b9ab4b52fdc46376e1339ed456c8
diff --git a/.gitmodules b/.gitmodules
index 00eeb89..5e10dfb 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -13,3 +13,6 @@
 [submodule "submodules/boost"]
 	path = submodules/boost
 	url = ../../github/boostorg/boost
+[submodule "submodules/libyang"]
+	path = submodules/libyang
+	url = ../../github/CESNET/libyang