data tree NEW opaque data node

Used for unknown anyxml/anydata nodes.
Some refactoring including making context
const for cases when only the dictionary
is modified or replacing unsigned int with
uint32_t.
diff --git a/src/xpath.c b/src/xpath.c
index f9a8009..e84bad9 100644
--- a/src/xpath.c
+++ b/src/xpath.c
@@ -298,7 +298,7 @@
  * @return LY_ERR
  */
 static LY_ERR
-cast_string_realloc(struct ly_ctx *ctx, uint16_t needed, char **str, uint16_t *used, uint16_t *size)
+cast_string_realloc(const struct ly_ctx *ctx, uint16_t needed, char **str, uint16_t *used, uint16_t *size)
 {
     if (*size - *used < needed) {
         do {
@@ -4127,13 +4127,13 @@
 
     if (mod && name) {
         switch (set->format) {
-        case LYD_UNKNOWN:
+        case LYD_SCHEMA:
             rc = asprintf(&str, "%s:%s", lys_prefix_find_module(set->local_mod, mod), name);
             break;
         case LYD_JSON:
             rc = asprintf(&str, "%s:%s", mod->name, name);
             break;
-        default:
+        case LYD_XML:
             LOGINT_RET(set->ctx);
         }
         LY_CHECK_ERR_RET(rc == -1, LOGMEM(set->ctx), LY_EMEM);
@@ -5164,7 +5164,7 @@
         pref_len = ptr - *qname;
 
         switch (set->format) {
-        case LYD_UNKNOWN:
+        case LYD_SCHEMA:
             /* schema, search all local module imports */
             mod = lys_module_find_prefix(set->local_mod, *qname, pref_len);
             break;
@@ -5174,7 +5174,7 @@
             mod = ly_ctx_get_module(set->ctx, str, NULL);
             free(str);
             break;
-        default:
+        case LYD_XML:
             LOGINT_RET(set->ctx);
         }