patch 8.1.1776: text added with a job isn't displayed

Problem:    Text added with a job to another buffer isn't displayed.
Solution:   Update topline after adding a line. (closes #4745)
diff --git a/src/testdir/check.vim b/src/testdir/check.vim
index 7f37f1c..48dbd85 100644
--- a/src/testdir/check.vim
+++ b/src/testdir/check.vim
@@ -21,3 +21,19 @@
     throw 'Skipped: ' .. a:name .. ' function missing'
   endif
 endfunc
+
+" Command to check for running on MS-Windows
+command CheckMSWindows call CheckMSWindows()
+func CheckMSWindows()
+  if !has('win32')
+    throw 'Skipped: only works on MS-Windows'
+  endif
+endfunc
+
+" Command to check for running on Unix
+command CheckUnix call CheckUnix()
+func CheckUnix()
+  if !has('unix')
+    throw 'Skipped: only works on Unix'
+  endif
+endfunc