Changes the crypto module to use unsigned char instead of byte. The byte
typedef is no longer included in the global namespace in crypto++ 6.0.0.
See https://github.com/weidai11/cryptopp/issues/442.
Fixes#184.
A CryptoPP::CFB_Mode<CryptoPP::AES>::Encryption was allocated at the
beginning of encoder_state_encode_leaf and was never freed. This commit
changes encoder_state_worker_encode_lcu to delete the CFB_Mode. Also
moves crypto handle from encoder_state_config_tile_t to encoder_state_t
so that it can be safely deleted without affecting other threads in the
same tile.