Update the cipher(1) documentation to explicitly state that the RSA cipher

string means the same a kRSA.
Reviewed-by: NAndy Polyakov <appro@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2821)

doc/man1/ciphers.pod

@@ -219,7 +219,8 @@ When in doubt, include B<!aNULL> in your cipherlist.
 
 =item B<kRSA>, B<aRSA>, B<RSA>
 
-Cipher suites using RSA key exchange, authentication or either respectively.
+Cipher suites using RSA key exchange or authentication. B<RSA> is an alias for
+B<kRSA>.
 
 =item B<kDHr>, B<kDHd>, B<kDH>