patch 8.2.1660: assert functions require passing expected as first argument

Problem:    Assert functions require passing expected result as the first
            argument, which isn't obvious.
Solution:   Use a method, as in "runtest()->assert_equal(expected)".
diff --git a/src/version.c b/src/version.c
index e815f66..47b1e56 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1660,
+/**/
     1659,
 /**/
     1658,