patch 8.0.1637: no test for term_dumpdiff() options argument

Problem:    No test for term_dumpdiff() options argument.
Solution:   Add a test.
diff --git a/src/version.c b/src/version.c
index 71a67ce..0249efb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -767,6 +767,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1637,
+/**/
     1636,
 /**/
     1635,