patch 8.2.3936: no proper test for maintaining change mark in diff mode

Problem:    No proper test for maintaining change mark in diff mode.
Solution:   Run the test with internal and external diff. (Sean Dewar,
            closes #9424)
diff --git a/src/version.c b/src/version.c
index 6849bd9..8aebc2c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3936,
+/**/
     3935,
 /**/
     3934,