[MEDIUM] implement the CSV output for the statistics

It is now possible to get CSV ouput from the statistics by
simply appending ";csv" to the HTTP request sent to get the
stats. The fields keep the same ordering as in the HTML page,
and a field "pxname" has been prepended at the beginning of
the line.
diff --git a/src/proto_http.c b/src/proto_http.c
index 82b8cea..7077df5 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -3387,7 +3387,8 @@
 	}
 	else if (s->data_source == DATA_SRC_STATS) {
 		/* dump server statistics */
-		int ret = stats_dump_http(s, s->be->uri_auth, 0);
+		int ret = stats_dump_http(s, s->be->uri_auth,
+					  (s->flags & SN_STAT_FMTCSV) ? 0 : STAT_FMT_HTML);
 		if (ret >= 0)
 			return ret;
 		/* -1 indicates an error */
@@ -4694,6 +4695,15 @@
 		}
 	}
 
+	h = t->req->data + txn->req.sl.rq.u + uri_auth->uri_len;
+	while (h <= t->req->data + txn->req.sl.rq.u + txn->req.sl.rq.u_l - 4) {
+		if (memcmp(h, ";csv", 4) == 0) {
+			t->flags |= SN_STAT_FMTCSV;
+			break;
+		}
+		h++;
+	}
+
 	/* we are in front of a interceptable URI. Let's check
 	 * if there's an authentication and if it's valid.
 	 */