Documentation: Remove XHTML spec and fix errors (#1547)

* Documentation: Remove XHTML spec and fix errors
None of the docs follow the XHTML specification, which means
that programs that expect this (such as Gnome Web) as it is advertised
as such, will completely fail to parse it as it is incorrect syntax. So
it is removed.

* Remove .chm files

doc/html/ru/Supported Systems for System Encryption.html

@@ -1,6 +1,5 @@
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
-    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="ru" lang="ru">
+<!DOCTYPE html>
+<html lang="ru">
 <head>
 <meta http-equiv="content-type" content="text/html; charset=utf-8" />
 <title>VeraCrypt - Бесплатное надёжное шифрование дисков с открытым исходным кодом</title>
@@ -49,10 +48,10 @@ Windows 10 </li></ul>
 Windows RT, Windows 2003 IA-64, Windows 2008 IA-64, Windows XP IA-64 и встроенные/планшетные версии Windows.
 </span></div>
 <div style="text-align:left; margin-top:19px; margin-bottom:19px; padding-top:0px; padding-bottom:0px">
-См. также раздел <a href="Supported%20Operating%20Systems.html" style="text-align:left; color:#0080c0; text-decoration:none.html">
+См. также раздел <a href="Supported%20Operating%20Systems.html" style="text-align:left; color:#0080c0; text-decoration:none">
 Поддерживаемые операционные системы</a></div>
 <div style="text-align:left; margin-top:19px; margin-bottom:19px; padding-top:0px; padding-bottom:0px">
 &nbsp;</div>
 <div style="text-align:left; margin-top:19px; margin-bottom:19px; padding-top:0px; padding-bottom:0px">
-<a href="VeraCrypt%20Rescue%20Disk.html" style="text-align:left; color:#0080c0; text-decoration:none; font-weight:bold.html">Следующий раздел &gt;&gt;</a></div>
+<a href="VeraCrypt%20Rescue%20Disk.html" style="text-align:left; color:#0080c0; text-decoration:none; font-weight:bold">Следующий раздел &gt;&gt;</a></div>
 </div><div class="ClearBoth"></div></body></html>