patch 8.0.0437: packadd test does not fully work

Problem:    The packadd test does not create the symlink correctly and does
            not test the right thing.
Solution:   Create the directory and symlink correctly.
diff --git a/src/testdir/test_packadd.vim b/src/testdir/test_packadd.vim
index 9d4c6d8..7dcaa60 100644
--- a/src/testdir/test_packadd.vim
+++ b/src/testdir/test_packadd.vim
@@ -71,11 +71,12 @@
 
 func Test_packadd_symlink_dir()
   if !has('unix')
-	  return
+    return
   endif
   let top2_dir = s:topdir . '/Xdir2'
   let real_dir = s:topdir . '/Xsym'
-  exec "silent !ln -s" real_dir top2_dir
+  call mkdir(real_dir, 'p')
+  exec "silent !ln -s Xsym"  top2_dir
   let &rtp = top2_dir . ',' . top2_dir . '/after'
   let &packpath = &rtp
 
diff --git a/src/version.c b/src/version.c
index 870b66b..413c2c1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    437,
+/**/
     436,
 /**/
     435,