patch 9.1.0785: cannot preserve error position when setting quickfix list

Problem:  cannot preserve error position when setting quickfix lists
Solution: Add the 'u' action for setqflist()/setloclist() and try
          to keep the closes target position (Jeremy Fleischman)

fixes: #15839
closes: #15841

Signed-off-by: Jeremy Fleischman <jeremyfleischman@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 15de27d..32167d6 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2024 Oct 12
+*builtin.txt*	For Vim version 9.1.  Last change: 2024 Oct 14
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -9766,6 +9766,8 @@
 			clear the list: >
 				:call setqflist([], 'r')
 <
+		'u'	Like 'r', but tries to preserve the current selection
+			in the quickfix list.
 		'f'	All the quickfix lists in the quickfix stack are
 			freed.