[MEDIUM] separate the http request from the session (step 1)

A struct http_req has been created to collect every information
related to an HTTP request being processed. Right now, it is
still in the struct session but the frontier is clear now.
diff --git a/src/log.c b/src/log.c
index 5079185..c8b3194 100644
--- a/src/log.c
+++ b/src/log.c
@@ -290,6 +290,7 @@
 	struct proxy *fe = s->fe;
 	struct proxy *be = s->be;
 	struct proxy *prx_log;
+	struct http_req *hreq = &s->hreq;
 	int log, tolog;
 	char *uri;
 	char *pxid;
@@ -350,9 +351,9 @@
 			for (hdr = 0; hdr < fe->nb_req_cap; hdr++) {
 				if (hdr)
 					*(h++) = '|';
-				if (s->hreq.cap[hdr] != NULL)
+				if (hreq->req.cap[hdr] != NULL)
 					h = encode_string(h, tmpline + sizeof(tmpline) - 7,
-							  '#', hdr_encode_map, s->hreq.cap[hdr]);
+							  '#', hdr_encode_map, hreq->req.cap[hdr]);
 			}
 			*(h++) = '}';
 		}