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/en/BLAKE2s-256.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="en" lang="en">
+<!DOCTYPE html>
+<html lang="en">
 <head>
 <meta http-equiv="content-type" content="text/html; charset=utf-8" />
 <title>VeraCrypt - Free Open source disk encryption with strong security for the Paranoid</title>
@@ -47,5 +46,5 @@ VeraCrypt uses only BLAKE2s with its maximum output size of 32-bytes (256 bits).
 </p>
 </div>
 <div style="text-align:left; margin-top:19px; margin-bottom:19px; padding-top:0px; padding-bottom:0px">
-<a href="SHA-256.html" style="text-align:left; color:#0080c0; text-decoration:none; font-weight:bold.html">Next Section &gt;&gt;</a></div>
+<a href="SHA-256.html" style="text-align:left; color:#0080c0; text-decoration:none; font-weight:bold">Next Section &gt;&gt;</a></div>
 </div><div class="ClearBoth"></div></body></html>