KeyObject for cipher symmetric key was being allocated improperly due to
an error in getting the key object size. Also added code to free
keyobject in the event of a key creation failure.
Windows 7 improved the memory management in CNG. To support Vista we
need to manage memory for cryptographic objects ourselves. This change
adds a key object memory pointer to the cipher context and adds code to
allocate and free it along with the key handle.
