OPTIM/MINOR: move the hdr_idx pools out of the proxy struct

It makes no sense to have one pointer to the hdr_idx pool in each proxy
struct since these pools do not depend on the proxy. Let's have a common
pool instead as it is already the case for other types.
diff --git a/include/proto/hdr_idx.h b/include/proto/hdr_idx.h
index 9e67a00..3de4361 100644
--- a/include/proto/hdr_idx.h
+++ b/include/proto/hdr_idx.h
@@ -1,23 +1,23 @@
 /*
-  include/proto/hdr_idx.h
-  This file defines function prototypes for fast header indexation.
-
-  Copyright (C) 2000-2006 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/hdr_idx.h
+ * This file defines function prototypes for fast header indexation.
+ *
+ * Copyright (C) 2000-2011 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_HDR_IDX_H
 #define _PROTO_HDR_IDX_H
@@ -25,6 +25,8 @@
 #include <common/config.h>
 #include <types/hdr_idx.h>
 
+extern struct pool_head *pool2_hdr_idx;
+
 /*
  * Initialize the list pointers.
  * list->size must already be set. If list->size is set and list->v is