libyang FEATURE introduce and use new ly_bool type

To indicate simple flags or true/false return values, use a standalone
ly_bool type.

We do not use stdbool's bool type to avoid need to mimic all its
features on platforms that do not provide it. ly_bool is just a simple
rename for uint8_t and the reason to use it is only a better readability
of the meaning of the variables or function's return values.
diff --git a/src/diff.c b/src/diff.c
index a02c5dd..3e3dfbc 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -516,7 +516,7 @@
  * @return LY_ERR value.
  */
 static LY_ERR
-lyd_diff_siblings_r(const struct lyd_node *first, const struct lyd_node *second, uint16_t options, uint8_t nosiblings,
+lyd_diff_siblings_r(const struct lyd_node *first, const struct lyd_node *second, uint16_t options, ly_bool nosiblings,
         struct lyd_node **diff)
 {
     LY_ERR ret = LY_SUCCESS;
@@ -669,7 +669,7 @@
 }
 
 static LY_ERR
-lyd_diff(const struct lyd_node *first, const struct lyd_node *second, uint16_t options, uint8_t nosiblings, struct lyd_node **diff)
+lyd_diff(const struct lyd_node *first, const struct lyd_node *second, uint16_t options, ly_bool nosiblings, struct lyd_node **diff)
 {
     const struct ly_ctx *ctx;