[MEDIUM] stats: add an admin level

The stats web interface must be read-only by default to prevent security
holes. As it is now allowed to enable/disable servers, a new keyword
"stats admin" is introduced to activate this admin level, conditioned by ACLs.
(cherry picked from commit 5334bab92ca7debe36df69983c19c21b6dc63f78)
diff --git a/include/proto/dumpstats.h b/include/proto/dumpstats.h
index 7038f46..9cf5eec 100644
--- a/include/proto/dumpstats.h
+++ b/include/proto/dumpstats.h
@@ -33,6 +33,7 @@
 #define STAT_SHOW_INFO  0x00000004	/* dump the info part */
 #define STAT_HIDE_DOWN  0x00000008	/* hide 'down' servers in the stats page */
 #define STAT_NO_REFRESH 0x00000010	/* do not automatically refresh the stats page */
+#define STAT_ADMIN      0x00000020	/* indicate a stats admin level */
 #define STAT_BOUND      0x00800000	/* bound statistics to selected proxies/types/services */
 
 #define STATS_TYPE_FE  0
@@ -58,6 +59,7 @@
 #define STAT_STATUS_DONE "DONE"	/* the action is successful */
 #define STAT_STATUS_NONE "NONE"	/* nothing happened (no action chosen or servers state didn't change) */
 #define STAT_STATUS_EXCD "EXCD"	/* an error occured becayse the buffer couldn't store all data */
+#define STAT_STATUS_DENY "DENY"	/* action denied */
 
 
 int stats_accept(struct session *s);