patch 9.1.0285: Still problems with cursor position for CTRL-D/U

Problem:  Problems with cursor position when scrolling half a page.
Solution: Rework the cursor logic. (Luuk van Baal)

closes: #14455

Signed-off-by: Luuk van Baal <luukvbaal@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_scroll_opt.vim b/src/testdir/test_scroll_opt.vim
index e09c240..cda9bf0 100644
--- a/src/testdir/test_scroll_opt.vim
+++ b/src/testdir/test_scroll_opt.vim
@@ -1028,10 +1028,10 @@
   call assert_equal(415, col('.'))
   exe "norm! \<C-D>"
   call assert_equal(520, winsaveview().skipcol)
-  call assert_equal(535, col('.'))
+  call assert_equal(615, col('.'))
   exe "norm! \<C-D>"
   call assert_equal(520, winsaveview().skipcol)
-  call assert_equal(735, col('.'))
+  call assert_equal(815, col('.'))
   exe "norm! \<C-D>"
   call assert_equal(520, winsaveview().skipcol)
   call assert_equal(895, col('.'))
@@ -1043,10 +1043,10 @@
   call assert_equal(495, col('.'))
   exe "norm! \<C-U>"
   call assert_equal(0, winsaveview().skipcol)
-  call assert_equal(375, col('.'))
+  call assert_equal(295, col('.'))
   exe "norm! \<C-U>"
   call assert_equal(0, winsaveview().skipcol)
-  call assert_equal(175, col('.'))
+  call assert_equal(95, col('.'))
   exe "norm! \<C-U>"
   call assert_equal(0, winsaveview().skipcol)
   call assert_equal(15, col('.'))