patch 9.0.1656: syntax test fails when detected shell type differs

Problem:    Syntax test fails when detected shell type differs.
Solution:   Avoid using "/bin/sh", it depends on the system.  Add a check that
            the shell type detection is correct.
diff --git a/src/version.c b/src/version.c
index fed49d9..535afe7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1656,
+/**/
     1655,
 /**/
     1654,