schema tree OPTIMIZE refactor enum to start at 0 instead of -1

Then it can be optimized with PACKED attribute.

Author: michalvasko

src/tree_schema.h

@@ -814,7 +814,6 @@ struct lys_submodule {
  * @brief YANG built-in types
  */
 typedef enum {
-    LY_TYPE_UNKNOWN = -1, /**< Unknown type (used in edit-config leaves) */
     LY_TYPE_DER = 0,      /**< Derived type */
     LY_TYPE_BINARY,       /**< Any binary data ([RFC 6020 sec 9.8](http://tools.ietf.org/html/rfc6020#section-9.8)) */
     LY_TYPE_BITS,         /**< A set of bits or flags ([RFC 6020 sec 9.7](http://tools.ietf.org/html/rfc6020#section-9.7)) */
@@ -835,6 +834,7 @@ typedef enum {
     LY_TYPE_UINT32,       /**< 32-bit unsigned integer ([RFC 6020 sec 9.2](http://tools.ietf.org/html/rfc6020#section-9.2)) */
     LY_TYPE_INT64,        /**< 64-bit signed integer ([RFC 6020 sec 9.2](http://tools.ietf.org/html/rfc6020#section-9.2)) */
     LY_TYPE_UINT64,       /**< 64-bit unsigned integer ([RFC 6020 sec 9.2](http://tools.ietf.org/html/rfc6020#section-9.2)) */
+    LY_TYPE_UNKNOWN,      /**< Unknown type (used in edit-config leaves) */
 } LY_DATA_TYPE;
 #define LY_DATA_TYPE_COUNT 20 /**< Number of different types */