Temperature control using a DHT11
It's a bit hard to see, but 

DHT11;  


does not look like a correct statement, assuming DHT11 is a class (not a define like shown) it should be something like 

DHT11 dht; 


where dht is an instance and you can use that. 

Than in

DHT11.read(DHT11pin);


you should replace it by

dht.read(DHT11pin);