patch 8.1.0837: timer interrupting cursorhold and mapping not tested

Problem:    Timer interrupting cursorhold and mapping not tested.
Solution:   Add tests with timers. (Ozaki Kiichi, closes #3871)
diff --git a/src/version.c b/src/version.c
index dac3c62..6ceaf23 100644
--- a/src/version.c
+++ b/src/version.c
@@ -784,6 +784,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    837,
+/**/
     836,
 /**/
     835,