patch 9.0.1630: "make clean" at the toplevel fails

Problem:    "make clean" at the toplevel fails.
Solution:   Clean the indent and syntax directories in a sub-shell.  (Ben
            Jackson, closes #12536, closes #12526)
diff --git a/src/version.c b/src/version.c
index c753acd..51e2e6e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1630,
+/**/
     1629,
 /**/
     1628,