patch 8.1.0994: relative cursor position is not calculated correctly

Problem:    Relative cursor position is not calculated correctly.
Solution:   Always set topline, also when window is one line only.
            (Robert Webb) Add more info to getwininfo() for testing.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 0d996c5..7cecab0 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -5762,6 +5762,8 @@
     dict_add_number(dict, "winid", wp->w_id);
     dict_add_number(dict, "height", wp->w_height);
     dict_add_number(dict, "winrow", wp->w_winrow + 1);
+    dict_add_number(dict, "topline", wp->w_topline);
+    dict_add_number(dict, "botline", wp->w_botline - 1);
 #ifdef FEAT_MENU
     dict_add_number(dict, "winbar", wp->w_winbar_height);
 #endif