Add ciphers doc

doc/man1/ciphers.pod

@@ -405,6 +405,21 @@ permissible.
 
 =back
 
+=head1 EQUAL PREFERENCE GROUPS
+
+If configuring a server, one may also configure equal-preference groups to
+partially respect the client's preferences when
+B<SSL_OP_CIPHER_SERVER_PREFERENCE> is enabled. Ciphers in an equal-preference
+group have equal priority and use the client order. This may be used to
+enforce that AEADs are preferred but select AES-GCM vs. ChaCha20-Poly1305
+based on client preferences. An equal-preference is specified with square
+brackets, combining multiple selectors separated by |. For example:
+
+ [ECDHE-ECDSA-CHACHA20-POLY1305|ECDHE-ECDSA-AES128-GCM-SHA256]
+ 
+ Once an equal-preference group is used, future directives must be
+ opcode-less.
+
 =head1 CIPHER SUITE NAMES
 
 The following lists give the SSL or TLS cipher suites names from the

doc/test.patch

@@ -0,0 +1,24 @@
+--- ciphers.pod	2018-04-09 02:53:14.337756676 +0900
++++ ciphers2.pod	2018-04-09 02:53:03.060663965 +0900
+@@ -405,6 +405,21 @@
+ 
+ =back
+ 
++=head1 EQUAL PREFERENCE GROUPS
++
++If configuring a server, one may also configure equal-preference groups to
++partially respect the client's preferences when
++B<SSL_OP_CIPHER_SERVER_PREFERENCE> is enabled. Ciphers in an equal-preference
++group have equal priority and use the client order. This may be used to
++enforce that AEADs are preferred but select AES-GCM vs. ChaCha20-Poly1305
++based on client preferences. An equal-preference is specified with square
++brackets, combining multiple selectors separated by |. For example:
++
++ [ECDHE-ECDSA-CHACHA20-POLY1305|ECDHE-ECDSA-AES128-GCM-SHA256]
++ 
++ Once an equal-preference group is used, future directives must be
++ opcode-less.
++
+ =head1 CIPHER SUITE NAMES
+ 
+ The following lists give the SSL or TLS cipher suites names from the