MEDIUM: http: add support for action "set-log-level" in http-request/http-response

Some users want to disable logging for certain non-important requests such as
stats requests or health-checks coming from another equipment. Other users want
to log with a higher importance (eg: notice) some special traffic (POST requests,
authenticated requests, requests coming from suspicious IPs) or some abnormally
large responses.

This patch responds to all these needs at once by adding a "set-log-level" action
to http-request/http-response. The 8 syslog levels are supported, as well as "silent"
to disable logging.
diff --git a/include/types/proto_http.h b/include/types/proto_http.h
index b50375f..b201055 100644
--- a/include/types/proto_http.h
+++ b/include/types/proto_http.h
@@ -247,6 +247,7 @@
 	HTTP_REQ_ACT_SET_HDR,
 	HTTP_REQ_ACT_REDIR,
 	HTTP_REQ_ACT_SET_NICE,
+	HTTP_REQ_ACT_SET_LOGL,
 	HTTP_REQ_ACT_MAX /* must always be last */
 };
 
@@ -258,6 +259,7 @@
 	HTTP_RES_ACT_ADD_HDR,
 	HTTP_RES_ACT_SET_HDR,
 	HTTP_RES_ACT_SET_NICE,
+	HTTP_RES_ACT_SET_LOGL,
 	HTTP_RES_ACT_MAX /* must always be last */
 };
 
@@ -371,6 +373,7 @@
 		} hdr_add;                     /* args used by "add-header" and "set-header" */
 		struct redirect_rule *redir;   /* redirect rule or "http-request redirect" */
 		int nice;                      /* nice value for HTTP_REQ_ACT_SET_NICE */
+		int loglevel;                  /* log-level value for HTTP_REQ_ACT_SET_LOGL */
 	} arg;                                 /* arguments used by some actions */
 };
 
@@ -385,6 +388,7 @@
 			struct list fmt;       /* log-format compatible expression */
 		} hdr_add;                     /* args used by "add-header" and "set-header" */
 		int nice;                      /* nice value for HTTP_RES_ACT_SET_NICE */
+		int loglevel;                  /* log-level value for HTTP_RES_ACT_SET_LOGL */
 	} arg;                                 /* arguments used by some actions */
 };