MEDIUM: config: inform the user only once that "redispatch" is deprecated

It may go away in 1.6, but there's no point reporting it for each and
every occurrence.
diff --git a/include/types/global.h b/include/types/global.h
index eff4ed3..82a8e9d 100644
--- a/include/types/global.h
+++ b/include/types/global.h
@@ -175,6 +175,7 @@
 /* bit values to go with "warned" above */
 #define WARN_BLOCK_DEPRECATED       0x00000001
 #define WARN_REQSETBE_DEPRECATED    0x00000002
+#define WARN_REDISPATCH_DEPRECATED  0x00000004
 
 /* to be used with warned and WARN_* */
 static inline int already_warned(unsigned int warning)
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 7356408..6ac3ccc 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -4062,7 +4062,8 @@
 		if (warnifnotcap(curproxy, PR_CAP_BE, file, linenum, args[0], NULL))
 			err_code |= ERR_WARN;
 
-		Warning("parsing [%s:%d]: keyword '%s' is deprecated, please use 'option redispatch' instead.\n",
+		if (!already_warned(WARN_REDISPATCH_DEPRECATED))
+			Warning("parsing [%s:%d]: keyword '%s' is deprecated in favor of 'option redispatch', and will not be supported by future versions.\n",
 				file, linenum, args[0]);
 		err_code |= ERR_WARN;
 		/* enable reconnections to dispatch */