patch 7.4.1558
Problem:    It is not easy to find out what windows display a buffer.
Solution:   Add win_findbuf().
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 6e18df4..1460731 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -2149,6 +2149,7 @@
 virtcol( {expr})		Number	screen column of cursor or mark
 visualmode( [expr])		String	last visual mode used
 wildmenumode()			Number	whether 'wildmenu' mode is active
+win_findbuf( {bufnr}) 		List	find windows containing {bufnr}
 win_getid( [{win} [, {tab}]]) 	Number	get window ID for {win} in {tab}
 win_gotoid( {expr})		Number	go to window with ID {expr}
 win_id2tabwin( {expr})		List	get tab and window nr from window ID
@@ -7176,6 +7177,10 @@
 		(Note, this needs the 'wildcharm' option set appropriately).
 
 
+win_findbuf({bufnr})					*win_findbuf()*
+		Returns a list with window IDs for windows that contain buffer
+		{bufnr}.  When there is none the list is empty.
+
 win_getid([{win} [, {tab}]])				*win_getid()*
 		Get the window ID for the specified window.
 		When {win} is missing use the current window.