Well I got:-
.....................libraries/DHT11/dht11.h:19:22: error: WProgram.h: No such file or directory
sketch_may16a.ino: In member function 'int dht11::read(int)':
sketch_may16a:48: error: 'DHTLIB_ERROR_TIMEOUT' was not declared in this scope
sketch_may16a:52: error: 'DHTLIB_ERROR_TIMEOUT' was not declared in this scope
sketch_may16a:59: error: 'DHTLIB_ERROR_TIMEOUT' was not declared in this scope
sketch_may16a:65: error: 'DHTLIB_ERROR_TIMEOUT' was not declared in this scope
sketch_may16a:83: error: 'DHTLIB_ERROR_CHECKSUM' was not declared in this scope
sketch_may16a:84: error: 'DHTLIB_OK' was not declared in this scope
Which would imply it is an old library.