patch 8.1.2356: rand() does not use the best algorithm

Problem:    rand() does not use the best algorithm.
Solution:   use xoshiro128** instead of xorshift. (Kaito Udagawa,
            closes #5279)
diff --git a/src/version.c b/src/version.c
index 4ca5c0f..7abb190 100644
--- a/src/version.c
+++ b/src/version.c
@@ -738,6 +738,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2356,
+/**/
     2355,
 /**/
     2354,