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/printer_lyb.c b/src/printer_lyb.c
index 0f5cf76..e45a919 100644
--- a/src/printer_lyb.c
+++ b/src/printer_lyb.c
@@ -38,9 +38,11 @@
 
 /**
  * @brief Hash table equal callback for checking hash equality only.
+ *
+ * Implementation of ::values_equal_cb.
  */
-static uint8_t
-lyb_hash_equal_cb(void *UNUSED(val1_p), void *UNUSED(val2_p), uint8_t UNUSED(mod), void *UNUSED(cb_data))
+static ly_bool
+lyb_hash_equal_cb(void *UNUSED(val1_p), void *UNUSED(val2_p), ly_bool UNUSED(mod), void *UNUSED(cb_data))
 {
     /* for this purpose, if hash matches, the value does also, we do not want 2 values to have the same hash */
     return 1;
@@ -48,9 +50,11 @@
 
 /**
  * @brief Hash table equal callback for checking value pointer equality only.
+ *
+ * Implementation of ::values_equal_cb.
  */
-static uint8_t
-lyb_ptr_equal_cb(void *val1_p, void *val2_p, uint8_t UNUSED(mod), void *UNUSED(cb_data))
+static ly_bool
+lyb_ptr_equal_cb(void *val1_p, void *val2_p, ly_bool UNUSED(mod), void *UNUSED(cb_data))
 {
     struct lysc_node *val1 = *(struct lysc_node **)val1_p;
     struct lysc_node *val2 = *(struct lysc_node **)val2_p;
@@ -379,7 +383,7 @@
  * @return LY_ERR value.
  */
 static LY_ERR
-lyb_write_string(const char *str, size_t str_len, uint8_t with_length, struct ly_out *out, struct lylyb_ctx *lybctx)
+lyb_write_string(const char *str, size_t str_len, ly_bool with_length, struct ly_out *out, struct lylyb_ctx *lybctx)
 {
     if (!str) {
         str = "";