patch 8.1.0184: not easy to figure out the window layout

Problem:    Not easy to figure out the window layout.
Solution:   Add "wincol" and "winrow" to what getwininfo() returns.
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index bd538d5..9394ece 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -4994,8 +4994,10 @@
 			variables	a reference to the dictionary with
 					window-local variables
 			width		window width
+			wincol		leftmost screen column of the window
 			winid		|window-ID|
 			winnr		window number
+			winrow		topmost screen column of the window
 
 		To obtain all window-local variables use: >
 			gettabwinvar({tabnr}, {winnr}, '&')