doc: Fix Texinfo docs; remove krb4 references

doc/whatis.texi

@@ -29,28 +29,6 @@ services can authenticate each other.
 
 @section Basic mechanism
 
-@ifinfo
-@macro sub{arg}
-<\arg\>
-@end macro
-@end ifinfo
-
-@iftex
-@macro sub{arg}
-@textsubscript{\arg\}
-@end macro
-@end iftex
-
-@ifhtml
-@macro sub{arg}
-
-@html
-<sub>\arg\</sub>
-@end html
-
-@end macro
-@end ifhtml
-
 @c ifdocbook
 @c macro sub{arg}
 @c docbook
@@ -133,8 +111,10 @@ It would be possible to add a @dfn{replay cache}
 to the server side.  The idea is to save the authenticators sent during
 the last few minutes, so that @var{B} can detect when someone is trying
 to retransmit an already used message. This is somewhat impractical
-(mostly regarding efficiency), and is not part of Kerberos 4; MIT
-Kerberos 5 contains it.
+(mostly regarding performance); MIT Kerberos 5 has a replay cache,
+while Heimdal does not.
+
+However, most GSS-API applicatons do not need a replay cache at all.
 
 To authenticate @var{B}, @var{A} might request that @var{B} sends
 something back that proves that @var{B} has access to the session