patch 9.0.1649: syntax test failure causes script to abort

Problem:    Syntax test failure causes script to abort.
Solution:   Fix appending string to list.

runtime/syntax/testdir/runtest.vim

@@ -163,7 +163,7 @@ for fname in glob('input/*.*', 1, 1)
 
       call delete('done/' .. root)
 
-      call failed_tests->extend(root)
+      eval failed_tests->add(root)
       if len(failed_tests) > MAX_FAILED_COUNT
 	call Message('')
 	call Message('Too many errors, aborting')

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1649,
 /**/
     1648,
 /**/