patch 9.0.0948: 'ttyfast' is set for arbitrary terminals

Problem:    'ttyfast' is set for arbitrary terminals.
Solution:   Always set 'ttyfast'. (closes #11549)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index c730527..83a4904 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -8569,10 +8569,7 @@
 	xterm entries...).
 
 				     *'ttyfast'* *'tf'* *'nottyfast'* *'notf'*
-'ttyfast' 'tf'		boolean	(default off, on when 'term' is xterm, hpterm,
-					sun-cmd, screen, rxvt, dtterm or
-					iris-ansi; also on when running Vim in
-					a DOS console)
+'ttyfast' 'tf'		boolean	(default on)
 			global
 	Indicates a fast terminal connection.  More characters will be sent to
 	the screen for redrawing, instead of using insert/delete line
@@ -8582,6 +8579,14 @@
 	line for lines that wrap.  This helps when using copy/paste with the
 	mouse in an xterm and other terminals.
 
+	The default used to be set only for some terminal names, but these
+	days nearly all terminals are fast, therefore the default is now "on".
+	If you have a slow connection you may want to set this option off,
+	e.g. depending on the host name: >
+		if hostname() =~ 'faraway'
+		   set nottyfast
+		endif
+<
 						*'ttymouse'* *'ttym'*
 'ttymouse' 'ttym'	string	(default depends on 'term')
 			global