patch 8.1.2154: quickfix window height wrong when there is a tabline

Problem:    Quickfix window height wrong when there is a tabline. (Daniel
            Hahler)
Solution:   Take the tabline height into account. (closes #5058)
diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index e0ab2b3..84cdb6c 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -297,6 +297,18 @@
   quit
 endfunc
 
+func Test_copenHeight_tabline()
+  set tabline=foo showtabline=2
+  copen
+  wincmd H
+  let height = winheight(0)
+  copen 10
+  call assert_equal(height, winheight(0))
+  quit
+  set tabline& showtabline&
+endfunc
+
+
 " Tests for the :cfile, :lfile, :caddfile, :laddfile, :cgetfile and :lgetfile
 " commands.
 func XfileTests(cchar)