[MAJOR] session: don't clear buffer status flags anymore

We want to be able to keep information about errors and timeouts
as long as possible in the buffer. Let's not clear these flags
anymore and keep them static. This does not seem to cause any
trouble, though a finer review might be wise.
diff --git a/src/session.c b/src/session.c
index 659dadb..71a4cb0 100644
--- a/src/session.c
+++ b/src/session.c
@@ -778,8 +778,6 @@
 			sess_set_term_flags(s);
 		}
 
-		s->req->flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
-		flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
 		if ((s->req->flags ^ flags) & BF_MASK_STATIC)
 			resync = 1;
 	}
@@ -901,8 +899,6 @@
 	if ((s->req->flags ^ rqf_last) & BF_MASK_STATIC)
 		resync = 1;
 
-	s->req->flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
-
 	/* according to benchmarks, it makes sense to resync now */
 	if (s->req->prod->state == SI_ST_DIS || s->req->cons->state == SI_ST_DIS)
 		goto resync_stream_interface;
@@ -925,8 +921,7 @@
 		    !(s->rep->flags & BF_FULL)) {
 			s->rep->hijacker(s, s->rep);
 		}
-		s->rep->flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
-		flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
+
 		if ((s->rep->flags ^ flags) & BF_MASK_STATIC)
 			resync = 1;
 	}
@@ -956,8 +951,6 @@
 			sess_set_term_flags(s);
 		}
 
-		s->rep->flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
-		flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
 		if ((s->rep->flags ^ flags) & BF_MASK_STATIC)
 			resync = 1;
 	}
@@ -1044,8 +1037,6 @@
 	if ((s->rep->flags ^ rpf_last) & BF_MASK_STATIC)
 		resync = 1;
 
-	s->rep->flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
-
 	if (s->req->prod->state == SI_ST_DIS || s->req->cons->state == SI_ST_DIS)
 		goto resync_stream_interface;
 
@@ -1096,8 +1087,8 @@
 		if (s->req->cons->state == SI_ST_EST)
 			stream_sock_data_finish(s->req->cons);
 
-		s->req->flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
-		s->rep->flags &= BF_CLEAR_READ & BF_CLEAR_WRITE & BF_CLEAR_TIMEOUT;
+		s->req->flags &= ~(BF_READ_NULL|BF_READ_PARTIAL|BF_WRITE_NULL|BF_WRITE_PARTIAL);
+		s->rep->flags &= ~(BF_READ_NULL|BF_READ_PARTIAL|BF_WRITE_NULL|BF_WRITE_PARTIAL);
 		s->si[0].prev_state = s->si[0].state;
 		s->si[1].prev_state = s->si[1].state;
 		s->si[0].flags &= ~(SI_FL_ERR|SI_FL_EXP);