[Groff] Add a history link to roff(7)

[Jan Stary]

The page "History of UNIX Manpages" http://manpages.bsd.lv/history.html
is more comprehensive than troff.org, contains links to the old material
and correspondence with the actual authors.

        Jan


diff --git a/man/roff.7.man b/man/roff.7.man
index a9a62e3..512c323 100644
--- a/man/roff.7.man
+++ b/man/roff.7.man
@@ -1162,11 +1162,21 @@ are documented in great detail.
 .\" --------------------------------------------------------------------
 .
 .TP
+History of UNIX Manpages
+.UR http://\:manpages.bsd.lv/\:history.html
+The history page
+.UE
+of the mdocml project provides an overview of
+.IR roff
+development up to date, with links to original documentation
+and comments of the original authors.
+.
+.TP
 troff.org
 .UR http://\:www.troff.org
 The historical troff site
 .UE
-provides an overview and pointers to all historical aspects of
+provides an overview and pointers to the historical aspects of
 .IR roff .
 .
 .TP