[BUG] debug: correctly report truncated messages

By using msg->sol as the beginning of a message, wrong messages were
displayed in debug mode when they were truncated on the last line,
because msg->sol points to the beginning of the last line. Use
data+msg->som instead.
diff --git a/src/proto_http.c b/src/proto_http.c
index ad95e56..5471ab5 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -2413,7 +2413,7 @@
 		     (msg->msg_state >= HTTP_MSG_BODY || msg->msg_state == HTTP_MSG_ERROR))) {
 		char *eol, *sol;
 
-		sol = msg->sol;
+		sol = req->data + msg->som;
 		eol = sol + msg->sl.rq.l;
 		debug_hdr("clireq", s, sol, eol);
 
@@ -4337,7 +4337,7 @@
 		     (msg->msg_state >= HTTP_MSG_BODY || msg->msg_state == HTTP_MSG_ERROR))) {
 		char *eol, *sol;
 
-		sol = msg->sol;
+		sol = rep->data + msg->som;
 		eol = sol + msg->sl.st.l;
 		debug_hdr("srvrep", s, sol, eol);