Included patch for persistent undo. Lots of changes and added test.
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 5b5e8fa..2a2d601 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -6053,6 +6053,7 @@
osfiletype Compiled with support for osfiletypes |+osfiletype|
path_extra Compiled with up/downwards search in 'path' and 'tags'
perl Compiled with Perl interface.
+persistent_undo Compiled with support for persistent undo history.
postscript Compiled with PostScript file printing.
printer Compiled with |:hardcopy| support.
profile Compiled with |:profile| support.