Doc update - legacy provider's cipher algorithms

doc/man3/EVP_des_cbc.pod

@@ -54,6 +54,10 @@ EVP_des_ofb()
 DES in CBC, ECB, CFB with 64-bit shift, CFB with 1-bit shift, CFB with 8-bit
 shift and OFB modes.
 
+None of these algorithms are provided by the OpenSSL default provider.
+To use them it is necessary to load either the OpenSSL legacy provider or another
+implementation.
+
 =item EVP_des_ede(),
 EVP_des_ede_cbc(),
 EVP_des_ede_cfb(),

doc/man3/EVP_desx_cbc.pod

@@ -23,6 +23,10 @@ All modes below use a key length of 128 bits and acts on blocks of 128-bits.
 
 The DES-X algorithm in CBC mode.
 
+This algorithm is not provided by the OpenSSL default provider.
+To use it is necessary to load either the OpenSSL legacy provider or another
+implementation.
+
 =back
 
 =head1 RETURN VALUES

doc/man7/OSSL_PROVIDER-legacy.pod

@@ -52,6 +52,32 @@ The OpenSSL legacy provider supports these operations and algorithms:
 
 =back
 
+=head2 Symmetric Ciphers
+
+Not all of these symmetric cipher algorithms are enabled by default.
+
+=over 4
+
+=item Blowfish
+
+=item CAST
+
+=item DES
+
+=item IDEA
+
+=item RC2
+
+=item RC4
+
+=item RC5
+
+Disabled by default. Use I<enable-rc5> config option to enable.
+
+=item SEED
+
+=back
+
 =begin comment
 
 When algorithms for other operations start appearing, the