patch 8.1.2019: 'cursorline' always highlights the whole line

Problem:    'cursorline' always highlights the whole line.
Solution:   Add 'cursorlineopt' to specify what is highlighted.
            (closes #4693)
diff --git a/runtime/optwin.vim b/runtime/optwin.vim
index 7d3a880..1eaf5ef 100644
--- a/runtime/optwin.vim
+++ b/runtime/optwin.vim
@@ -429,6 +429,9 @@
   call append("$", "cursorline\thighlight the screen line of the cursor")
   call append("$", "\t(local to window)")
   call <SID>BinOptionL("cul")
+  call append("$", "cursorlineopt\tspecifies which area 'cursorline' highlights")
+  call append("$", "\t(local to window)")
+  call <SID>OptionL("culopt")
   call append("$", "colorcolumn\tcolumns to highlight")
   call append("$", "\t(local to window)")
   call <SID>OptionL("cc")