dict FEATURE detect errors in lydict_remove

Redundant macro FREE_STRING removed.
diff --git a/src/dict.h b/src/dict.h
index 68e1081..7874813 100644
--- a/src/dict.h
+++ b/src/dict.h
@@ -107,8 +107,11 @@
  * @param[in] value String to be freed. Note, that not only the string itself
  * must match the stored value, but also the address is being compared and the
  * counter is decremented only if it matches. If NULL, function does nothing.
+ * @return LY_SUCCESS if the value was found and removed (or refcount decreased).
+ * @return LY_ENOTFOUND if the value was not found.
+ * @return LY_ERR on other errors.
  */
-void lydict_remove(const struct ly_ctx *ctx, const char *value);
+LY_ERR lydict_remove(const struct ly_ctx *ctx, const char *value);
 
 /** @} dict */