CLEANUP: connection: remove the now unused CS_FL_REOS flag

Let's remove it before it gets uesd again. It was mostly replaced with
CS_FL_EOI and by mux-specific states or flags.
diff --git a/contrib/debug/flags.c b/contrib/debug/flags.c
index 986f8cf..dc2a5b7 100644
--- a/contrib/debug/flags.c
+++ b/contrib/debug/flags.c
@@ -160,7 +160,6 @@
 	SHOW_FLAG(f, CS_FL_NOT_FIRST);
 	SHOW_FLAG(f, CS_FL_WAIT_FOR_HS);
 	SHOW_FLAG(f, CS_FL_EOI);
-	SHOW_FLAG(f, CS_FL_REOS);
 	SHOW_FLAG(f, CS_FL_EOS);
 	SHOW_FLAG(f, CS_FL_ERR_PENDING);
 	SHOW_FLAG(f, CS_FL_WANT_ROOM);
diff --git a/include/proto/connection.h b/include/proto/connection.h
index 915be87..3e4a1ef 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -513,7 +513,7 @@
 	if (cs->flags & CS_FL_EOS)
 		cs->flags |= CS_FL_ERROR;
 	else
-		cs->flags |= CS_FL_REOS | CS_FL_ERR_PENDING;
+		cs->flags |= CS_FL_ERR_PENDING;
 }
 
 /* detect sock->data read0 transition */
diff --git a/include/types/connection.h b/include/types/connection.h
index 49ec6d5..7e253e0 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -93,7 +93,7 @@
 	CS_FL_WANT_ROOM     = 0x00000400,  /* More bytes to transfert, but not enough room */
 	CS_FL_ERR_PENDING   = 0x00000800,  /* An error is pending, but there's still data to be read */
 	CS_FL_EOS           = 0x00001000,  /* End of stream delivered to data layer */
-	CS_FL_REOS          = 0x00002000,  /* End of stream received (buffer not empty) */
+	/* unused: 0x00002000 */
 	CS_FL_EOI           = 0x00004000,  /* end-of-input reached */
 	/* unused: 0x00008000 */
 	CS_FL_WAIT_FOR_HS   = 0x00010000,  /* This stream is waiting for handhskae */
diff --git a/src/backend.c b/src/backend.c
index 28ed993..a9e20e0 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1230,7 +1230,7 @@
 		if (!srv_conn->target || srv_conn->target == s->target) {
 			srv_conn->flags &= ~(CO_FL_ERROR | CO_FL_SOCK_RD_SH | CO_FL_SOCK_WR_SH);
 			if (srv_cs)
-				srv_cs->flags &= ~(CS_FL_ERROR | CS_FL_EOS | CS_FL_REOS);
+				srv_cs->flags &= ~(CS_FL_ERROR | CS_FL_EOS);
 			reuse = 1;
 			old_conn = srv_conn;
 		} else {