MINOR: stream-int: replace si_cant_put() with si_rx_room_{blk,rdy}()

Remaining calls to si_cant_put() were all for lack of room and were
turned to si_rx_room_blk(). A few places where SI_FL_RXBLK_ROOM was
cleared by hand were converted to si_rx_room_rdy().

The now unused si_cant_put() function was removed.
diff --git a/src/memory.c b/src/memory.c
index ced9af5..17ac1d1 100644
--- a/src/memory.c
+++ b/src/memory.c
@@ -514,7 +514,7 @@
 
 	dump_pools_to_trash();
 	if (ci_putchk(si_ic(si), &trash) == -1) {
-		si_cant_put(si);
+		si_rx_room_blk(si);
 		return 0;
 	}
 	return 1;