MINOR: ssl: Don't abuse ssl_options.

A bind_conf does contain a ssl_bind_conf, which already has a flag to know
if early data are activated, so use that, instead of adding a new flag in
the ssl_options field.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index cf0d696..b63ceb4 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -847,6 +847,10 @@
   next line in the configuration file sees the new environment. See also
   "setenv", "presetenv", and "unsetenv".
 
+ssl-allow-0rtt
+  Allow using 0RTT on every listener. 0RTT is prone to various attacks, so be
+  sure to know the security implications before activating it.
+
 stats bind-process [ all | odd | even | <number 1-64>[-<number 1-64>] ] ...
   Limits the stats socket to a certain set of processes numbers. By default the
   stats socket is bound to all processes, causing a warning to be emitted when