patch 8.2.2363: curpos() does not accept a string argument as before

Problem:    curpos() does not accept a string argument as before.
solution:   Make a string argument work again. (Yegappan Lakshmanan,
            closes #7690

src/testdir/test_cursor_func.vim

@@ -25,6 +25,9 @@ func Test_move_cursor()
   " below last line goes to last line
   eval [9, 1]->cursor()
   call assert_equal([4, 1, 0, 1], getcurpos()[1:])
+  " pass string arguments
+  call cursor('3', '3')
+  call assert_equal([3, 3, 0, 3], getcurpos()[1:])
 
   call setline(1, ["\<TAB>"])
   call cursor(1, 1, 1)