MINOR: log: add a new flag 'L' for locally processed requests

People who use "option dontlog-normal" are bothered with redirects and
stats being logged and reported as errors in the logs ("PR" = proxy
blocked the request).

This patch introduces a new flag 'L' for when a request is locally
processed, that is not considered as an error by the log filters. That
way we know a request was intercepted and processed by haproxy without
logging the line when "option dontlog-normal" is in effect.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 269c129..bd55745 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -11651,8 +11651,10 @@
             connection limit enforcement, because a DENY filter was matched,
             because of a security check which detected and blocked a dangerous
             error in server response which might have caused information leak
-            (eg: cacheable cookie), or because the response was processed by
-            the proxy (redirect, stats, etc...).
+            (eg: cacheable cookie).
+
+        L : the session was locally processed by haproxy and was not passed to
+            a server. This is what happens for stats and redirects.
 
         R : a resource on the proxy has been exhausted (memory, sockets, source
             ports, ...). Usually, this appears during the connection phase, and
@@ -11837,6 +11839,9 @@
           closer to the average reported "Tw" timer, in order not to consume
           resources for just a few attackers.
 
+     LR   The request was intercepted and locally handled by haproxy. Generally
+          it means that this was a redirect or a stats request.
+
      SC   The server or an equipment between it and haproxy explicitly refused
           the TCP connection (the proxy received a TCP RST or an ICMP message
           in return). Under some circumstances, it can also be the network