libyang CHANGE add LY_VALUE_LYB

Add a separate value format of the LYB representation of the type.
Some of the callbacks API of the type plugins was modified to reflect the
need of passing generic (binary) data representation of the value.
diff --git a/src/path.c b/src/path.c
index 7ca8616..a4db50c 100644
--- a/src/path.c
+++ b/src/path.c
@@ -453,7 +453,8 @@
             break;
         case LY_VALUE_CANON:
         case LY_VALUE_XML:
-            /* not really defined */
+        case LY_VALUE_LYB:
+            /* not really defined or accepted */
             LOGINT_RET(ctx);
         }
     }