patch 9.0.0871: using freed memory when clearing augroup at more prompt

Problem:    Using freed memory when clearing augroup at more prompt.
Solution:   Delay clearing augroup until it's safe. (closes #11441)
diff --git a/src/version.c b/src/version.c
index 73c106e..b57fffe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    871,
+/**/
     870,
 /**/
     869,