[MEDIUM] separate protocol-level accept() from the frontend's

For a long time we had two large accept() functions, one for TCP
sockets instanciating proxies, and another one for UNIX sockets
instanciating the stats interface.

A lot of code was duplicated and both did not work exactly the same way.

Now we have a stream_sock layer accept() called for either TCP or UNIX
sockets, and this function calls the frontend-specific accept() function
which does the rest of the frontend-specific initialisation.

Some code is still duplicated (session & task allocation, stream interface
initialization), and might benefit from having an intermediate session-level
accept() callback to perform such initializations. Still there are some
minor differences that need to be addressed first. For instance, the monitor
nets should only be checked for proxies and not for other connection templates.

Last, we renamed l->private as l->frontend. The "private" pointer in
the listener is only used to store a frontend, so let's rename it to
eliminate this ambiguity. When we later support detached listeners
(eg: FTP), we'll add another field to avoid the confusion.
diff --git a/include/proto/stream_sock.h b/include/proto/stream_sock.h
index 929cb08..d0d172f 100644
--- a/include/proto/stream_sock.h
+++ b/include/proto/stream_sock.h
@@ -1,23 +1,23 @@
 /*
-  include/proto/stream_sock.h
-  This file contains client-side definitions.
-
-  Copyright (C) 2000-2008 Willy Tarreau - w@1wt.eu
-
-  This library is free software; you can redistribute it and/or
-  modify it under the terms of the GNU Lesser General Public
-  License as published by the Free Software Foundation, version 2.1
-  exclusively.
-
-  This library is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-  Lesser General Public License for more details.
-
-  You should have received a copy of the GNU Lesser General Public
-  License along with this library; if not, write to the Free Software
-  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
-*/
+ * include/proto/stream_sock.h
+ * This file contains client-side definitions.
+ *
+ * Copyright (C) 2000-2010 Willy Tarreau - w@1wt.eu
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
 
 #ifndef _PROTO_STREAM_SOCK_H
 #define _PROTO_STREAM_SOCK_H
@@ -31,6 +31,7 @@
 
 
 /* main event functions used to move data between sockets and buffers */
+int stream_sock_accept(int fd);
 int stream_sock_read(int fd);
 int stream_sock_write(int fd);
 void stream_sock_data_finish(struct stream_interface *si);