koi8-r.7: Charset pages unification, minor cleanups

- adjust references
- remove stray comments, streamline description
  (charsets(7) and Wikipedia provide more detailed
   and up-to-date description)
- list differences between koi8-r.7 vs koi8-u.7
- cosmetics

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man7/koi8-r.7

@@ -1,8 +1,6 @@
 '\" t -*- coding: UTF-8 -*-
 .\" Copyright 2001      Alexey Mahotkin <alexm@hsys.msk.ru>
 .\"
-.\" Lots of text ripped from http://koi8.pp.ru/
-.\"
 .\" %%%LICENSE_START(GPLv2+_DOC_FULL)
 .\" This is free documentation; you can redistribute it and/or
 .\" modify it under the terms of the GNU General Public License as
@@ -25,31 +23,13 @@
 .\" %%%LICENSE_END
 .\"
 .TH KOI8-R 7 2014-02-16 "Linux" "Linux Programmer's Manual"
-.nh
 .SH NAME
-koi8-r \- Russian character set encoded in octal, decimal, and
-hexadecimal
+koi8-r \- Russian character set encoded in octal, decimal,
+and hexadecimal
 .SH DESCRIPTION
-KOI8-R is the character set of choice for encoding Russian texts for
-many UNIX-like operation systems.
-KOI8-R is a successor for KOI-8, a
-de-facto standard for Internet Mail, News, WWW, and other interactive
-services at least all over the ex-SU territory.
-.PP
-KOI8-R is defined by RFC\ 1489 (Registration of a Cyrillic Character
-Set).
-.SH NOTES
-KOI8-R was designed for mixed Russian/English texts and covers
-only Russian Cyrillic characters,
-so if you're looking for Cyrillic characters for Ukrainian,
-Byelorussian, and so on,
-try ISO-IR-111, or KOI8-U
-(Ukrainian Character Set), or KOI8-C (for ancient Russian texts)
-instead, which are identical to KOI8-R in the Russian Cyrillic letters
-area.
-.PP
-A more complete set of Cyrillic characters is also defined by the
-ISO-8859-5 character set.
+RFC\ 1489 defines an 8-bit character set, KOI8-R. 
+KOI8-R encodes the
+characters used in Russian.
 .SS KOI8-R characters
 The following table displays the characters in KOI8-R, which
 are printable and unlisted in the
@@ -196,11 +176,12 @@ T}
 376	254	FE	Ч	CYRILLIC CAPITAL LETTER CHE
 377	255	FF	Ъ	CYRILLIC CAPITAL LETTER HARD SIGN
 .TE
+.SH NOTES
+The differences with KOI8-U are in the hex positions
+A4, A6, A7, AD, B4, B6, B7, and BD.
 .SH SEE ALSO
 .BR ascii (7),
-.BR iso-8859-5 (7),
-.BR koi8-u (7)
-
-RFC\ 1489,
-.UR http://koi8.pp.ru/
-.UE
+.BR charsets (7),
+.BR iso_8859-5 (7),
+.BR koi8-u (7),
+.BR utf-8 (7)