Update s_client and s_server documentation about some missing arguments

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1837)
diff --git a/apps/s_server.c b/apps/s_server.c
index 9858413..ee66318 100644
--- a/apps/s_server.c
+++ b/apps/s_server.c
@@ -684,7 +684,7 @@
     {"port", OPT_PORT, 'p',
      "TCP/IP port to listen on for connections (default is " PORT ")"},
     {"accept", OPT_ACCEPT, 's',
-     "TCP/IP optional host and port to accept on (default is " PORT ")"},
+     "TCP/IP optional host and port to listen on for connections (default is *:" PORT ")"},
 #ifdef AF_UNIX
     {"unix", OPT_UNIX, 's', "Unix domain socket to accept on"},
 #endif