Fatigue fracture of an engine cylinder resulting in a loss of power on the left engine. Additional causes were the pilot's failure to maintain minimum control airspeed (Vmc), the resulting loss of aircraft control, and an inadvertent stall/spin. Contributing factors were the pilot's failure to feather the propeller on the failed engine and his decision to turn toward the inoperative engine during the circling maneuver. Additional factors were the inoperative hydraulic system pump and the emergency landing gear actuation which caused the pilot to circle prior to landing.