Add forgotten header file

include/ejabberd_sm.hrl

@@ -0,0 +1,7 @@
+-record(session, {sid, usr, us, priority, info}).
+-record(session_counter, {vhost, count}).
+-type sid() :: {erlang:timestamp(), pid()}.
+-type ip() :: {inet:ip_address(), inet:port_number()} | undefined.
+-type info() :: [{conn, atom()} | {ip, ip()} | {node, atom()}
+                 | {oor, boolean()} | {auth_module, atom()}].
+-type prio() :: undefined | integer().