patch 8.1.1280: remarks about functionality not in Vi clutters the help

Problem:    Remarks about functionality not in Vi clutters the help.
Solution:   Move all info about what is new in Vim or already existed in Vi to
            vi_diff.txt.  Remove {not in Vi} remarks. (closes #4268) Add
            "noet" to the help files modeline.  Also include many other help
            file improvements.
diff --git a/runtime/doc/quickfix.txt b/runtime/doc/quickfix.txt
index ef084fa..6d9b342 100644
--- a/runtime/doc/quickfix.txt
+++ b/runtime/doc/quickfix.txt
@@ -1,4 +1,4 @@
-*quickfix.txt*  For Vim version 8.1.  Last change: 2019 Jan 13
+*quickfix.txt*  For Vim version 8.1.  Last change: 2019 May 05
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -16,8 +16,6 @@
 8. The directory stack			|quickfix-directory-stack|
 9. Specific error file formats		|errorformats|
 
-{Vi does not have any of these commands}
-
 The quickfix commands are not available when the |+quickfix| feature was
 disabled at compile time.
 
@@ -502,7 +500,6 @@
 			autocommand event is disabled by adding it to
 			'eventignore'.  This considerably speeds up editing
 			each buffer.
-			{not in Vi}
 			Also see |:bufdo|, |:tabdo|, |:argdo|, |:windo|,
 			|:ldo|, |:cfdo| and |:lfdo|.
 
@@ -515,7 +512,6 @@
 				:{cmd}
 				etc.
 <			Otherwise it works the same as `:cdo`.
-			{not in Vi}
 
 							*:ldo*
 :ld[o][!] {cmd}		Execute {cmd} in each valid entry in the location list
@@ -528,7 +524,6 @@
 				etc.
 <			Only valid entries in the location list are used.
 			Otherwise it works the same as `:cdo`.
-			{not in Vi}
 
 							*:lfdo*
 :lfdo[!] {cmd}		Execute {cmd} in each file in the location list for
@@ -540,7 +535,6 @@
 				:{cmd}
 				etc.
 <			Otherwise it works the same as `:ldo`.
-			{not in Vi}
 
 =============================================================================
 2. The error window					*quickfix-window*