patch 8.2.3640: freeze when calling term_wait() in a close callback

Problem:    Freeze when calling term_wait() in a close callback.
Solution:   Set a "closing" flag to tell term_wait() to return. (closes #9152)
diff --git a/src/version.c b/src/version.c
index 6162d87..a83ff61 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3640,
+/**/
     3639,
 /**/
     3638,