patch 8.0.1427: the :leftabove modifier doesn't work for :copen

Problem:    The :leftabove modifier doesn't work for :copen.
Solution:   Respect the split modifier. (Yegappan Lakshmanan, closes #2496)
diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index 0787e60..fb78f69 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -3078,3 +3078,30 @@
   augroup END
   enew | only
 endfunc
+
+" Test for the position of the quickfix and location list window
+func Test_qfwin_pos()
+  " Open two windows
+  new | only
+  new
+  cexpr ['F1:10:L10']
+  copen
+  " Quickfix window should be the bottom most window
+  call assert_equal(3, winnr())
+  close
+  " Open at the very top
+  wincmd t
+  topleft copen
+  call assert_equal(1, winnr())
+  close
+  " open left of the current window
+  wincmd t
+  below new
+  leftabove copen
+  call assert_equal(2, winnr())
+  close
+  " open right of the current window
+  rightbelow copen
+  call assert_equal(3, winnr())
+  close
+endfunc