vim-patch:8.1.0994: fix relative cursor position #9676

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.
8fcb60f961

runtime/doc/eval.txt

@@ -4504,11 +4504,13 @@ getwininfo([{winid}])					*getwininfo()*
 		tab pages is returned.
 
 		Each List item is a Dictionary with the following entries:
+			botline		last displayed buffer line
 			bufnr		number of buffer in the window
 			height		window height (excluding winbar)
 			loclist		1 if showing a location list
 			quickfix	1 if quickfix or location list window
 			tabnr		tab page number
+			topline		first displayed buffer line 
 			variables	a reference to the dictionary with
 					window-local variables
 			width		window width