libyang CHANGE use LY_ARRAY_SIZE_TYPE for iterator variables in LY_TREE_FOR

Because of the change in sized arrays design (780ade2101), also the
iterators and other variables used with LY_TREE_FOR or LY_TREE_SIZE
should be of LY_ARRAY_SIZE_TYPE.

Also the new LY_PRI_ARRAY_SIZE_TYPE was introduced to correctly print
the value of this type in a formatted print functions.
diff --git a/src/xml.c b/src/xml.c
index 8a9a3da..f376672 100644
--- a/src/xml.c
+++ b/src/xml.c
@@ -1064,7 +1064,8 @@
 lyxml_get_prefixes(struct lyxml_ctx *xmlctx, const char *value, size_t value_len, struct ly_prefix **val_prefs)
 {
     LY_ERR ret;
-    uint32_t u, c;
+    LY_ARRAY_SIZE_TYPE u;
+    uint32_t c;
     const struct lyxml_ns *ns;
     const char *start, *stop;
     struct ly_prefix *prefixes = NULL;
@@ -1118,7 +1119,7 @@
 lyxml_value_compare(const char *value1, const struct ly_prefix *prefs1, const char *value2, const struct ly_prefix *prefs2)
 {
     const char *ptr1, *ptr2, *ns1, *ns2;
-    uint32_t u1, u2;
+    LY_ARRAY_SIZE_TYPE u1, u2;
     int len;
 
     if (!value1 && !value2) {