Update runtime files.
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 1dd7491..d216f0c 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt* For Vim version 8.1. Last change: 2019 Sep 18
+*options.txt* For Vim version 8.1. Last change: 2019 Sep 26
VIM REFERENCE MANUAL by Bram Moolenaar
@@ -8177,8 +8177,8 @@
Win32 and OS/2)
global or local to buffer |global-local|
Maximum number of changes that can be undone. Since undo information
- is kept in memory, higher numbers will cause more memory to be used
- (nevertheless, a single change can use an unlimited amount of memory).
+ is kept in memory, higher numbers will cause more memory to be used.
+ Nevertheless, a single change can already use a large amount of memory.
Set to 0 for Vi compatibility: One level of undo and "u" undoes
itself: >
set ul=0