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/tree.h b/src/tree.h
index eb0fd71..135bcad 100644
--- a/src/tree.h
+++ b/src/tree.h
@@ -237,7 +237,8 @@
     LY_VALUE_SCHEMA,          /**< YANG schema value, prefixes map to YANG import prefixes */
     LY_VALUE_SCHEMA_RESOLVED, /**< resolved YANG schema value, prefixes map to module structures directly */
     LY_VALUE_XML,             /**< XML data value, prefixes map to XML namespace prefixes */
-    LY_VALUE_JSON             /**< JSON data value, prefixes map to module names */
+    LY_VALUE_JSON,            /**< JSON data value, prefixes map to module names */
+    LY_VALUE_LYB              /**< LYB data binary value, prefix mapping is type-specific (but usually like JSON) */
 } LY_VALUE_FORMAT;
 
 /** @} trees */