MEDIUM: cli: handle CLI level from the master CLI

Handle the CLI level in the master CLI. In order to do this, the master
CLI stores the level in the stream. Each command are prefixed by a
"user" or "operator" command before they are forwarded to the target
CLI.

The level can be configured in the haproxy program arguments with the
level keyword: -S /tmp/sock,level,admin -S /tmp/sock2,level,user.
diff --git a/include/types/stream.h b/include/types/stream.h
index cdd6a51..5e854c5 100644
--- a/include/types/stream.h
+++ b/include/types/stream.h
@@ -94,6 +94,7 @@
 
 
 /* flags for the proxy of the master CLI */
+/* 0x1.. to 0x3 are reserved for ACCESS_LVL_MASK */
 
 #define PCLI_F_PROMPT          0x4
 #define PCLI_F_PAYLOAD         0x8